COLLECTIVE REVIEW
Immunology and Lung Cancer E. Carmack Holmes, M.D.
ABSTRACT Carcinoma of the lung is the number one cancer killer in the United States. The overall cure rate is about lo%, and although resection is the best treatment available, five-year survival following operation is only 25%. Recent studies have shown that patients with lung cancer are immunosuppressed but that pulmonary tumors do contain tumor-associated antigens. Studies of other human tumors indicate that immunotherapy can augment tumor immunity and can be an effective surgical adjuvant. This communicationreviews the basic principles of tumor immunology, with emphasis on the immunology of lung cancer, and discusses how these principles may be applied to the therapy of lung cancer.
The importance of immunological factors in the progression of clinical cancer has become increasingly apparent over the past several years. Host immunocompetence has been emphasized, and immunodeficiency has been shown to be associated with an extremely poor prognosis in patients with cancer [lo]. The immunological aspects of several different human tumors have been extensively evaluated and immunotherapeutic modalities developed that have demonstrated their clinicaI effectiveness [23, 28, 291. Although lung cancer is the number one cancer killer in the United States, evaluation of its immunological aspects has lagged behind that of other neoplasms. The magnitude of the problem demands that new approaches be sought to attain better control of this disease. The overall survival of patients with lung cancer is only lo%, and the five-year survival following curative resection is 20 to 25% [25]. Whereas we From the Division of Oncology and the Divisicn of Thoracic Surgery, Department of Surgery, UCLA School of Medicine, Los Angeles, and the Surgical Services, Sepulveda Veterans Administration Hospital, Sepulveda, CA. Supported by US Public Health Service Grants no. CA 12582 and CA05252 and grants from the Surgical Services, Sepulveda Veterans Administration Hospital. Address reprint requests to Dr. Holmes, Division of Oncology, 54-140, UCLA School of Medicine, Los Angeles, CA 90024.
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would not accept a 75'/0 failure rate in the surgical treatment of duodenal ulcer disease or a 75% occlusion rate with coronary revascularization, apparently we are resigned to a 75% failure rate for surgical treatment of carcinoma of the lung. Certainly attempts have been made to enhance survival by extending the operative procedure and using adjuvant radiation therapy and chemotherapy; but these efforts have not resulted in improvement over conventional surgical treatment alone [8, 431. It is apparent that when patients with lung cancer seek treatment, they frequently have disseminated disease. While the metastasis is not always clinically detectable, survival statistics indicate that most patients have microscopic foci of disseminated disease prior to operation that the host is unable to control. Therefore, local extirpation of the neoplasm alone is inadequate for control of the disease, and some form of systemic antitumor therapy is necessary. The use of single-agent chemotherapy as an adjunct to resection has not increased survival [8, 431. Effective surgical adjuvant chemotherapy for breast cancer is available, and the results are very promising [12]. However, a consistently effective, minimally toxic chemotherapeutic agent for lung cancer is not available. If there were such an agent, the indications for surgical resection would be extended and a good case for radical extirpation could be made. Since it is well recognized in other human tumors and from animal studies that immunotherapy is effective only against a certain limited volume of tumor, it is clear that the role of immunotherapy will be as an adjunct to more ablative treatment. The surgeon can reduce the major portion of the tumor burden, and immunotherapy can be used postoperatively to "mop up" the remaining local and distant microscopic foci of disease. Recent observations suggest that patients with lung cancer are immunosuppressed compared with patients who have other neoplasms [7, 9, 15, 16, 24, 49,501. It is likely that this immunosuppression partly
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explains the extremely poor prognosis of patients with lung cancer, and therefore it seems logical that immunotherapeutic manipulations be studied in these patients. This review briefly restates the principles of human tumor immunology, with emphasis on the immunology of lung cancer, and points out how these principles can be applied clinically in an attempt to improve survival in patients with lung cancer.
Human Tumor Immunology The early study of animal tumor immunology, initiated by the classic work of Prehn and Main i n 1957 [341, provided the background for investigators to begin probing the immunology of human tumors. In the last ten years, a subject that was almost nonexistent prior to that time has proliferated incredibly. From these studies in human and animal systems, certain principles of tumor immunology have emerged. It has become increasingly apparent that immunocompetence has strong bearing on the clinical course of cancer. Immunocompetence has been measured by delayed cutaneous hypersensitivity to certain antigens; the ability of patients to respond to these antigens correlates closely with survival, stage of disease, and even resectability. In addition, the immunocompetence of the patient’s lymphocytes as measured by various in vitro assays has also been shown to relate to survival and stage of disease. It is not clear at present whether immunodeficiency precedes the development of a neoplasm or whether it is a direct result of the tumor [Ill. However, the evidence favors the concept that tumors elaborate certain immunosuppressive substances and that removing the bulk of the tumor improves immunocompetence. It is likely that some tumors elaborate more immunosuppressive substance than others, and therefore the level of immunocompetence varies not only according to the actual tumor volume, but according to the particular histological type. lmmunotherapeutic studies in animal and human systems have been very helpful in planning and coordinating clinical studies, and the efficacy of immunotherapy for certain human tumors has been well established. Its use in the treatment of certain skin tumors, such as
basal cell carcir.oma and squamous cell carcinoma of the skin, was developed by Klein [22]. The use of Calmette-Gu6rin bacillus (BCG) to control cutaneous melanoma by intralesional injection has been demonstrated by Morton and co-workers [29] and confirmed by many other investigators. These studies and extensive animal experiments indicate that immunotherapy is most effective when the immunostimulating agent comes into close contact with the tumor. Rapp, Zbar, and their associates [44, 511 have shown that injecting BCG into a tumor growing in the flank of a guinea pig induces regression of regional lymph node metastases from that tumor and results in permanent cure. This treatment is more effective than giving the immunostimulating agent at a site distant from the growing tumor. Human immunotherapy trials have also demonstrated that direct injection of immunostimulants into the tumor gives rise to better systemic antitumor immunity and is capable of controlling microscopic amounts of disseminated disease, similar to the animal model [281. In many clinical situations, and always with surgical adjuvant therapy, the tumor is not available for direct injection. Therefore the use of tumor cells propagated in tissue culture, mixed with BCG and injected intradermally into patients, has been studied as an alternative method for immunotherapy used as a surgical adjuvant. Preliminary results from our laboratory indicate that this treatment is effective.
Active and Passive Immunotherapy Immunotherapy can be administered in an active or passive form, and active immunotherapy may be either specific or nonspecific. In the specific form, the patient’s immune mechanisms are directed against specific tumor antigens. The antigen used may be living or irradiated whole tumor cells, cell fragments, or cell-free tumor antigens. Active nonspecific immunotherapy serves as a nonspecific stimulus to the immune response. Immunological adjuvants such as BCG, Corynebacteriurn pauzium, or levamisole hydrochloride are nonspecific immune stimulators and can augment humoral as well as cellular immunity to tumor antigens as well as to other antigens [3, 38, 42, 471. Passive or adoptive immunotherapy involves
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the transfer to the cancer patient of immune factors from another host of the same or a different species who has been immunized against tumor-associated antigens. This transfer may be in the form of serum antibodies, immune lymphoid cells, or subcellular fractions of lymphoid cells such as transfer factor or immune ribonucleic acid (RNA) [30, 321. One particularly appealing method of passive immunotherapy entails the transfer of informational molecules that can arouse a specific immune response in the recipient’s own immune system. The two substances known to have this remarkable ability are Lawrence’s transfer factor and immune RNA [30,32]. Transfer factor is capable of transferring immunity to skin grafts, purified protein derivative (PPD), and a variety of other antigens and is able to repair immune defects in certain immunodeficiency diseases. It has not been used extensively for cancer immunotherapy but has been helpful in the treatment of some disseminated fungal and viral diseases. The investigation of transfer factor is somewhat hampered by the fact that it can be obtained only from human donors, and there are currently no animal models in which this therapy can be evaluated. Immune RNA, extracted from the lymphoid tissues of a xenogeneic host following immunization with tumors, can induce immunity in syngeneic recipients of tumor transplants t371. Immune RNA is highly advantageous because it can be produced by immunizing a host other than man. The use of heterologous immune RNA to induce tumor immunity has been quite successful in animal models and is currently undergoing early clinical trials [32, 371. Though transfer factor and immune RNA are being evaluated in several centers, to date no objective therapeutic benefit has been consistently observed. It must be emphasized that the studies are only Phase I trials, and the complete therapeutic potential of these modalities is still unknown. Both methods of immunotherapy have considerable promise because each bypasses many of the problems associated with other types of passive and adoptive immunotherapy such as HL-A incompatibility, serum sickness, and anaphylaxis, to name a few. Finally, it should be mentioned that immunotherapy has been demonstrated to be a use-
ful adjunct to chemotherapy. Israel [20, 211 has shown that nonspecific immunotherapeutic stimulation can increase the response rate to chemotherapy and the duration of the response, markedly diminish the side-effects of chemotherapy, and also allow for administration of greater amounts of chemotherapy.
Tumor-Specific Antigens Another important aspect of the rapidly growing field of tumor immunology is the definition and purification of tumor-associated antigens that are characteristic of certain neoplasms. The best known of these antigens are carcinoembryonic antigen and alpha-fetal protein [14, 361, which can be detected in the plasma of patients with certain types of neoplasms. The quantity of the circulating antigen is directly related to the total tumor burden. These and similar antigens in other neoplasms must be further developed if immunotherapy is to be used in a prophylactic manner following resection. Since in this setting the disease is subclinical and cannot be measured by clinical means, the ability to monitor tumor burden-and thereby response to surgical adjuvant immunotherapy-by measurement of circulating tumor antigens is extremely valuable. Attempts are being made to isolate and purify tumor antigens in a variety of neoplasms for this purpose. General Principles of lmmunotherapy Several important principles have been developed from experience in animal and human studies: It is clear that immunotherapy is effective
against only a limited amount of disease. Therefore it will be most effective in clinical situations in which the majority of tumor burden has been reduced surgically so that immunotherapy can be initiated when the tumor burden is minimal. Nonspecific immunostimulating agents are most effective when injected directly into the tumor or administered with tumor cells, and the most potent systemic immunity results when the nonspecific immune stimulator comes into direct contact with tumor antigens.
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3 . The level of immunocompetence is directly cancer was originally suggested by the studies of related to prognosis and stage of disease, and Krant and associates [241. Further studies have efforts at reversing immunodeficiency states shown that reactivity to DNCB is directly related are very important. to prognosis, stage of disease, and even resect4. Specific tumor immunity can be transferred ability [49, 501. Interestingly, the reactivity to the with cell-free products, such as transfer factor recall antigens was essentially the same in paand immune RNA, and can be used to recon- tients with lung cancer as in normal people. stitute immunodeficiency states. Wells and co-workers [49, 501 studied 75 lung 5. Immunotherapeutic maneuvers should be cancer patients and 25 patients with benign lung designed to augment cell-mediated immu- disease and confirmed that more than 96% of nity selectively, since in some tumor systems those with benign disease were capable of becomstimulation of humoral antibody may serve to ing sensitized to and reacting to DNCB. Only 52% of the patients with lung cancer could be enhance tumor growth. Invitro techniques can be used to monitor the sensitized to DNCB. In addition, they found that 6. patient’s response to therapy by quantitating 70% of the patients with lung cancer who the amount of circulating tumor antigen. reacted to DNCB had resectable disease compared with only 3 DNCB-negative patients. It is clear that immunotherapy can be highly They also showed that survival was superior in effective in animal systems and in certain patients who reacted to DNCB. Another inhuman neoplasms. It is therefore appropriate teresting observation was that DNCB reactivity that the use of immunotherapy be evaluated exwas more suppressed in patients with squatensively in patients with lung cancer. mous cell carcinoma than in patients with Immunocompetence of Lung Cancer Patients adenocarcinoma. In our own studies of more When compared to the survival of patients with than 100 patients with pulmonary carcinoma we most other neoplasms, the prognosis for lung found that no patients with Stage I11 (dissemicancer is very poor and suggests that there is nated) disease were capable of reacting to something unique about the cancer or the pa- DNCB; however, 50% of these patients did retient which allows for rapid progression of the spond to one of the recall antigens. We tested 33 disease. These observations have led inves- patients preoperatively with DNCB and found tigators to evaluate the immunocompetence of that reactivity to DNCB was closely related to patients with lung cancer by studying their resectability. We have seen only 2 DNCBdelayed cutaneous hypersensitivity to 2,4- positive patients whose tumor was unresectable dinitrochlorobenzene (DNCB) and to the so- and 1DNCB-negative patient who had resectable called recall antigens (PPD, mumps, Candida, disease. In our studies the response to recall Varidase). Skin testing with DNCB involves ap- antigens did not relate to resectability. plying this chemical to the skin and allowing the The fact that the majority of lung cancer papatient to become sensitized to it over a two- tients are capable of reacting to the standard week period. The patient is then challenged recall antigens in a manner similar to patients with a second, smaller dose of DNCB, and the with benign disease, while at the same time cutaneous reactivity to the antigen is quanti- being unable to become sensitized to DNCB, tated. Testing with DNCB evaluates the pa- suggests that the immunological defect in patient’s ability to process a new antigen and gen- tients with lung cancer most likely lies in the erate an immune response to it and therefore afferent limb of the immune mechanism. Certests the afferent and efferent limbs of the im- tainly, correction of this immunological defimune response. Skin testing with a recall anti- ciency should lead to improved survival. gen tests immunological memory. Since most Since it is well known that lung cancers elabopatients have been previously sensitized to one rate biologically active substances such as of these four agents, recall antigens test only the parathyroid hormone, adrenocorticotropic efferent limb of the immune response. hormone, and serotonin [351, and since these Immunodeficiency in patients with lung cancers are known to be associated with a
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number of intriguing paraneoplastic syndromes, it is not unreasonable to suspect that lung tumors could also elaborate immunoregulatory substances. Such a substance has been described by Glasgow and colleagues [13], who showed that a highly immunosuppressive immune regulatory alpha (IRA) globulin is present in the plasma of cancer patients and is closely correlated with the inability to respond to DNCB. Sample and co-workers [41] have reported that serum from patients with cancer inhibits lymphocyte function in vitro. Of the 9 patients they studied who had the immunosuppressive substance in their serum, 2 had bronchogenic carcinoma. It is therefore possible, and perhaps likely, that lung tumors elaborate immunosuppressive substances and that resection of the neoplasm may well be associated with an improvement in the immunodeficiency state. A variety of in vitro tests have also been used to demonstrate immunodeficiency in patients with lung cancer. The ability of lymphocytes from patients with lung cancer to respond by increased DNA synthesis in the presence of various mitogens and antigens has been evaluated. A number of investigators [7,15,161 have shown that by these criteria, patients with lung cancer are profoundly immunodepressed and that lymphocytes from cancer patients are far from normal in their ability to undergo deoxyribonucleic acid synthesis in the presence of immunological stimuli in vitro. This interesting immunological lymphocyte defect is being extensively evaluated, and immunotherapeutic substances that will reverse the immune paralysis are being sought. In summary, it is clear that patients with lung cancer are immunodepressed and that this directly affects their prognosis. Treatment thus should be directed toward reversing immunosuppression. Extirpation of the tumor may be an important step in this process since it may serve to improve immunocompetence.
have been demonstrated by a variety of techniques, and these same methods have recently been applied to the study of human lung tumor antigens. While these antigens have not been as extensively investigated as those of other tumors such as colon cancer, sarcoma, breast cancer, and melanoma, in the recent past a number of investigators have detected tumor-associated antigens in lung cancer [5, 18, 19, 27, 31,39,46, 49, 501. Wells and associates [49, 501 have described an antigen present on the membrane of lung tumors that is capable of eliciting specific delayed cutaneous hypersensitivity reactions. In these studies, 9 of 16 patients with lung cancer had delayed cutaneous hypersensitivity to a lung tumor membrane antigen, whereas only 1 reacted to a membrane antigen derived from normal lung tissue. These studies indicate that lung tumors have antigens on their surface which are different from normal lung antigens and which are capable of eliciting delayed cutaneous hypersensitivity or cellular immunity in some patients with lung cancer. Several in vitro assays have been used to demonstrate antigens in pulmonary carcinoma that are both unique to the tumor and capable of eliciting an immune response in the host. These studies-which include leukocyte immobilization in agarose [5], leukocyte adherence inhibition,* stimulated protein synthesis [431, colony inhibition [18], lymphocyte blastogenesis [271, and immunodiffusion [31]-have all confirmed the presence of specific tumor antigens on the surface of lung tumor cells. They have also shown that a common antigen occurs in all lung cancers regardless of histological type, though evidence exists, too, that there may be other antigens which are unique to lung tumors of the various histological types [19,31]. These in vitro studies have also confirmed that the host is capable of responding immunologically against these tumor antigens, which are not present in corresponding normal lung. The majority of these studies are quite recent, and data regarding in vitro reactivity to lung tumor antigens as Lung Tumor Antigens it relates to stage of disease and prognosis are In order for immunotherapy to be effective, the not yet available. However, it would not be surtumor must contain antigens which are unique prising to find demonstrable in vitro lymphoto it and against which the patient can generate an immune response. Tumor-associated antigens *MM Urist and EC Holmes, report in preparation.
255 Collective Review: Holmes: Immunology and Lung Cancer
cyte immunity in patients who have progressive clinical disease. Since these assays are performed in vitro (in the absence of the patient’s serum), certain humoral factors that suppress lymphocyte activity in vivo may be lacking; these could be nonspecific immunosuppressing factors such as IRA [13] or specific blocking factors such as those described by Hellstrom and co-workers [17]. The presence of these factors may explain why in vitro cellular immunity is frequently observed in patients who have progressive disease. One of the most promising and exciting aspects of the study of lung tumor antigens involves their purification and chemical characterization. When these antigens have been sufficiently purified, they can be used to develop highly sensitive serological tests, such as radioimmunoassay, with which one can detect small amounts of circulating tumor antigen in the plasma. One can then monitor the response to therapy in patients with subclinical disease: rising levels of these circulating tumor antigens indicate early recurrence and reflect the response to various therapeutic attempts to control the disease. Tumor cells contain a number of different antigens, many of which are shared by various neoplasms of different histological types. For example, an antigenic site on carcinoembryonic antigen is present in the sera of a high percentage of lung cancer patients. The magnitude of elevation of this antigenic determinant in the patient’s serum is directly related to extent of disease and could be used to monitor possible occult recurrences before they are clinically detectable [6, 261.
Possibilities for Immunotherapy of Lung Cancer Although lung cancers contain antigens against which the host can react immunologically, patients with lung tumors are frequently immunosuppressed and are not capable of initiating an adequate immune response. It seems reasonable, therefore, to attempt to augment the host immune response to these antigens and to try to reverse the immunodepression of lung cancer. Indeed, surgical extirpation alone may play a very important role in reversing the im-
munodeficiency state by removing a possible source of immunosuppressive substances. There is clinical evidence that some patients with lung cancer are capable of reacting against their tumors. A few reports have appeared of spontaneous tumor regression in patients with bronchogenic carcinoma, and in 1 instance the patient’s lymphocytes were found to be strongly cytotoxic against lung cancer cells [4]. An intriguing report from Ruckdeschel and his colleagues [40] indicated improved survival in patients with resectable lung cancer who developed postoperative empyema compared with similar patients who did not. The difference in survival between the two populations was highly statistically significant. This experiment of nature suggests that perhaps surgical extirpation along with a potent nonspecific immunological stimulant to the regional lymph nodes such as chronic empyema has a beneficial effect on survival in patients with lung cancer. Animal experiments support these clinical impressions, indicating that systemic immunotherapy is capable of curtailing tumor growth within the pulmonary parenchyma. Baldwin and Pimm [l] evaluated the immunotherapy of pleural and pulmonary neoplasms in animal systems and found that intravenous BCG can prevent pulmonary metastases following intravenous injection of tumor cells. This effect was noted when BCG was given as late as seven days after the injection of tumor cells. Spontaneous pulmonary metastases following the removal of a transplanted neoplasm are also suppressed by intravenous administration of BCG. In addition, spontaneous metastases by a primary hepatoma have been prevented by intravenous injection of BCG [21. And finally, Baldwin and Pimm [33] have shown that intrapleurally injected BCG is capable of controlling actively growing pleural tumors; BCG injected intravenously, subcutaneously, or intraperitoneally had no effect on the growth of these tumors. As a result of these studies, clinical trials with intrapleural BCG are now being carried out in Belfast, Ireland, in patients with mesothelioma. While the animal immunotherapeutic experiments have not been directed toward a primary pulmonary neoplasm, BCG and C. parvurn do concentrate in the pul-
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monary parenchyma and are capable of inducing an antitumor response within it following their intravenous injection. The immunotherapy of human lung cancer can take one of several forms previously mentioned. To date, most ongoing trials involve active nonspecific immunotherapy. The results of immunotherapy for malignant melanoma following wide excision and removal of regional lymph node metastases is very encouraging for the prospect of effective immunotherapy of lung cancer, since these studies are based on the principle of surgical reduction of the tumor burden and use of immunotherapy prophylactically before clinical recurrence has developed [28]. Nonspecific immune-stimulating agents that are currently being evaluated in patients with lung cancer are BCG, C . parvum, and levamisole. All three have been shown to be effective immune stimulants in extensive animal investigations, and they have potent immunostimulating effects in patients [3, 28, 38, 42, 471. All these agents have been evaluated in Phase I trials; the toxicity has been carefully evaluated, and acceptable nontoxic doses and routes of administration have been determined. BCG is an attenuated, viable bovine tubercle bacillus and is usually supplied in a lyophilized state; the lyophilized material is reconstituted and administered to patients by intradermal injection. Corynebacterium parvum is a formalin-treated, killed bacterium that is usually administered by the intravenous route. These two agents are usually administered once weekly on an outpatient basis. Levamisole has a distinct advantage in that it is not an organism but a chemical. It is given orally in the form of a pill and is usually taken daily for three days every one or two weeks. Several ongoing clinical trials are being conducted in the United States and Europe to evaluate these three agents as surgical adjuvants following pulmonary resection. Some of these studies are well into their second year, and it is hoped that clinical data will be available in the near future. Active specific immunotherapy for lung cancer has lagged behind active nonspecific immunotherapy because lung cancer cells are difficult to propagate in tissue culture, making a constant and reliable source of tumor antigens
difficult to supply. However, with the development of soluble lung tumor antigens and improved tissue culture techniques, it is likely that active specific immunotherapy for lung cancer will become possible in the very near future. In addition, cell-free materials such as immune RNA can be developed and used in patients with lung cancer. However, trials with immune RNA and other specific active immunotherapeutic agents have just recently been initiated, and only a few studies evaluating immunotherapy in patients with lung cancer have been completed. Some investigators have administered BCG to patients with bronchogenic carcinoma and have observed tumor regression in up to 28%. In addition, survival in these patients was superior to that in controls [221. BCG has been combined with chemotherapy in patients who have lung cancer with a decidedly beneficial effect [48]. Finally, Takita and Brugarolas [45] treated 5 patients who had locally advanced bronchogenic carcinoma with an autologous tumor vaccine following incomplete surgical resection and considered this active specific immunotherapy responsible for improved survival in the treated group: 3 of 5 patients treated with the tumor vaccine were alive at eighteen months, whereas all 6 control patients had died by that time. While the immunotherapy of lung cancer is certainly in its infancy and reliable clinical results have not yet been reported, sufficient information is available from animal models, immunological studies in patients with lung cancer, and immunotherapy trials in patients with other neoplasms to suggest strongly that immunotherapy will have a role in the treatment of patients with lung cancer.
References 1. Baldwin RW, Pimm MV: BCG immunotherapy of pulmonary growths from intravenously transferred rat tumor cells. Br J Cancer 27:48, 1973 2. Baldwin RW, Pimm MV: BCG suppression of pulmonary metastases from primary rat hepatoma. Br J Cancer 30:473, 1974 3. Bast RC, Zbar B, Borsos T, et al: BCG and cancer. N Engl J Med 290:1413, 1974 4. Bell JW: Possible immune factors in spontaneous regression of bronchogenic carcinoma. Am J Surg 120:804, 1970 5 . Boddie AW, Holmes EC, Roth JA, et al: Detection
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of cell mediated immunity to soluble human lung cancer antigens. Int J Cancer 15:823, 1975 6. Broder LE, Walkes TP, Primack A, et al: Biologic markers in the evaluation of disease status of patients with advanced bronchogenic carcinoma. Proc Am Assoc Cancer Res 16:223, 1975 7. Brugarolas A, Han T, Takita H, et al: Immunologic assays in lung cancer. NY State J Med 73:747,1973 8. Brunner KW, Marthaler TH, Miller W: Effects of long-term adjuvant chemotherapy with cyclophosphamide for radically resected bronchogenic carcinoma. Cancer Chemother Rep 4:125, 1973 9. Ducos J, Migueres J, Colombies P: Lymphocyte response to PHA in patients with lung cancer. Lancet 1:1111, 1970 10. Eilber FR, Morton DL: Impaired immunologic reactivity and recurrence following cancer surgery. Cancer 25:362, 1970 11. Eilber FR, Nizze JA, Morton DL: Sequential evaluation of general immune competence in cancer patients: correlation with clinical cancer. Cancer 35:660, 1975 12. Fisher BR, Barbone P, Economou SC, et al: Phenylalanine mustard in the management of primary breast cancer. N Engl J Med 292:117, 1975 13. Glasgow AH, Nimberg RB, Menzoian JO: Association of anergy with an immunosuppressive peptide fraction in the serum of patients with cancer. N Engl J Med 291:1263, 1974 14. Gold P, Friedman SO: Specific carcinoembryonic antigens of the human digestive system. J Exp Med 122:467, 1965 15. Gross RL, Latty A, Williams E, et al: Abnormal spontaneous rosette formation and rosette inhibition in lung cancer. N Engl J Med 292:339, 1975 16. Han T, Takita H: Impaired lymphocyte response to allogeneic cultured lymphoid cells in patients with lung cancer. N Engl J Med 286:605, 1972 17. Hellstrom I, Hellstrom KE, Pierce GE, et al: Cellular and humoral immunity to different types of human neoplasms. Nature (London) 220:1352, 1968 18. Hellstrom I, Hellstrom KE, Sjogren HO, et al: Demonstration of cell mediated immunity to human neoplasms of various histological types. Int J Cancer 7:1, 1971 19. Hollinshead AC, Steward THM, Herberman RB: Delayed hypersensitivity reactions to soluble membrane antigens of human malignant lung cells. J Nat Cancer Inst 52:327, 1974 20. Israel L: Preliminary results of non-specific immunotherapy for lung cancer. Cancer Chemother Rep 4:283, 1973 21. Israel L, Edelstein RL: Non-specific immunostimulation with Corynebacteriurn parvum in human cancer, Immunological Aspects of Neoplasia. From the M. D. Anderson Hospital and
Tumor Institute. Baltimore, Williams & Wilkins, 1974 22. Khadzhiev S: Treatment of bronchial cancer patients with a water saline extract of BCG. Vope Onkol 17:51, 1971 23. Klein E: Hypersensitivity reactions at tumor sites. Cancer Res 27:2351, 1969 24. Krant JK, Manskopf G, Bandrup C, et al: Immunologic alterations in bronchogenic cancer. Cancer 21:573, 1968 25. Lee YN: Prognostic factors in surgical treatment of bronchogenic carcinoma. Surg Gynecol Obstet 135:961, 1972 26. LoGerfo P, Herter FP, Braun J, et al: Tumorassociated antigen with pulmonary neoplasms. Ann Surg 175:495, 1972 27. Mavligit GM, Gutterman JU, McBride CM, et al: Cell-mediated immunity to human solid tumors: in vitro detection by lymphocyte blastogenic responses to a cell-associated and solubilized tumor antigen. Nat Cancer Inst Monogr 37:167, 1973 28. Morton DL, Eilber FR, Holmes EC, et al: BCG immunotherapy of malignant melanoma. Ann Surg 180:635, 1974 29. Morton DL, Holmes EC, Eilber FR, et al: Immunological aspects of neoplasia: a rational basis for immunotherapy. Ann Intern Med 74:587,1971 30. Neidhart JA, LoBuglio AF: Transfer factor therapy of malignancy. Semin Oncol 1:379, 1974 31. Nordquist RE: Specific antigens in human alveolar cell carcinoma. Cancer Res 33:1790, 1973 32. Pilch YH, DeKernion J: Immunotherapy of cancer with immune RNA: current status. Semin Oncol 1:387, 1974 33. Pimm MV, Baldwin RW: BCG therapy of pleural and peritoneal growth of transplanted rat tumors. Int J Cancer (in press) 34. Prehn RT, Main JM: Immunity to methylcholanthrene-induced sarcomas. J Nat Cancer Inst 18:769, 1957 35. Primack A: The production of markers by bronchogenic carcinoma: a review. Semin Oncol 1:235, 1974 36. Purves LR, Bershon I, Geddes EW: Serum alpha fetal protein and primary cancer of the liver in man. Cancer 25:261, 1970 37. Ramming KP, Pilch YH: Mediation of immunity to tumor isografts in mice by heterologous ribonucleic acid. Science 168:492, 1970 38. Renoux G, Renoux M: Levamisole inhibits and cures a solid malignant tumor and its pulmonary metastases in mice. Nature New Biol 240:217, 1972 39. Roth JA, Holmes EC, Boddie AW, et al: Lymphocyte responses of lung cancer patients to tumorassociated antigen measured by leucine-incorporation. J Thorac Cardiovasc Surg 70:613, 1975 40. Ruckdeschel JC, Codish SD, Stranahan A, et al:
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Immunology and Lung Cancer E. Carmack Holmes, M.D.
ABSTRACT Carcinoma of the lung is the number one cancer killer in the United States. The overall cure rate is about lo%, and although resection is the best treatment available, five-year survival following operation is only 25%. Recent studies have shown that patients with lung cancer are immunosuppressed but that pulmonary tumors do contain tumor-associated antigens. Studies of other human tumors indicate that immunotherapy can augment tumor immunity and can be an effective surgical adjuvant. This communicationreviews the basic principles of tumor immunology, with emphasis on the immunology of lung cancer, and discusses how these principles may be applied to the therapy of lung cancer.
The importance of immunological factors in the progression of clinical cancer has become increasingly apparent over the past several years. Host immunocompetence has been emphasized, and immunodeficiency has been shown to be associated with an extremely poor prognosis in patients with cancer [lo]. The immunological aspects of several different human tumors have been extensively evaluated and immunotherapeutic modalities developed that have demonstrated their clinicaI effectiveness [23, 28, 291. Although lung cancer is the number one cancer killer in the United States, evaluation of its immunological aspects has lagged behind that of other neoplasms. The magnitude of the problem demands that new approaches be sought to attain better control of this disease. The overall survival of patients with lung cancer is only lo%, and the five-year survival following curative resection is 20 to 25% [25]. Whereas we From the Division of Oncology and the Divisicn of Thoracic Surgery, Department of Surgery, UCLA School of Medicine, Los Angeles, and the Surgical Services, Sepulveda Veterans Administration Hospital, Sepulveda, CA. Supported by US Public Health Service Grants no. CA 12582 and CA05252 and grants from the Surgical Services, Sepulveda Veterans Administration Hospital. Address reprint requests to Dr. Holmes, Division of Oncology, 54-140, UCLA School of Medicine, Los Angeles, CA 90024.
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would not accept a 75'/0 failure rate in the surgical treatment of duodenal ulcer disease or a 75% occlusion rate with coronary revascularization, apparently we are resigned to a 75% failure rate for surgical treatment of carcinoma of the lung. Certainly attempts have been made to enhance survival by extending the operative procedure and using adjuvant radiation therapy and chemotherapy; but these efforts have not resulted in improvement over conventional surgical treatment alone [8, 431. It is apparent that when patients with lung cancer seek treatment, they frequently have disseminated disease. While the metastasis is not always clinically detectable, survival statistics indicate that most patients have microscopic foci of disseminated disease prior to operation that the host is unable to control. Therefore, local extirpation of the neoplasm alone is inadequate for control of the disease, and some form of systemic antitumor therapy is necessary. The use of single-agent chemotherapy as an adjunct to resection has not increased survival [8, 431. Effective surgical adjuvant chemotherapy for breast cancer is available, and the results are very promising [12]. However, a consistently effective, minimally toxic chemotherapeutic agent for lung cancer is not available. If there were such an agent, the indications for surgical resection would be extended and a good case for radical extirpation could be made. Since it is well recognized in other human tumors and from animal studies that immunotherapy is effective only against a certain limited volume of tumor, it is clear that the role of immunotherapy will be as an adjunct to more ablative treatment. The surgeon can reduce the major portion of the tumor burden, and immunotherapy can be used postoperatively to "mop up" the remaining local and distant microscopic foci of disease. Recent observations suggest that patients with lung cancer are immunosuppressed compared with patients who have other neoplasms [7, 9, 15, 16, 24, 49,501. It is likely that this immunosuppression partly
251 Collective Review: Holmes: Immunology and Lung Cancer
explains the extremely poor prognosis of patients with lung cancer, and therefore it seems logical that immunotherapeutic manipulations be studied in these patients. This review briefly restates the principles of human tumor immunology, with emphasis on the immunology of lung cancer, and points out how these principles can be applied clinically in an attempt to improve survival in patients with lung cancer.
Human Tumor Immunology The early study of animal tumor immunology, initiated by the classic work of Prehn and Main i n 1957 [341, provided the background for investigators to begin probing the immunology of human tumors. In the last ten years, a subject that was almost nonexistent prior to that time has proliferated incredibly. From these studies in human and animal systems, certain principles of tumor immunology have emerged. It has become increasingly apparent that immunocompetence has strong bearing on the clinical course of cancer. Immunocompetence has been measured by delayed cutaneous hypersensitivity to certain antigens; the ability of patients to respond to these antigens correlates closely with survival, stage of disease, and even resectability. In addition, the immunocompetence of the patient’s lymphocytes as measured by various in vitro assays has also been shown to relate to survival and stage of disease. It is not clear at present whether immunodeficiency precedes the development of a neoplasm or whether it is a direct result of the tumor [Ill. However, the evidence favors the concept that tumors elaborate certain immunosuppressive substances and that removing the bulk of the tumor improves immunocompetence. It is likely that some tumors elaborate more immunosuppressive substance than others, and therefore the level of immunocompetence varies not only according to the actual tumor volume, but according to the particular histological type. lmmunotherapeutic studies in animal and human systems have been very helpful in planning and coordinating clinical studies, and the efficacy of immunotherapy for certain human tumors has been well established. Its use in the treatment of certain skin tumors, such as
basal cell carcir.oma and squamous cell carcinoma of the skin, was developed by Klein [22]. The use of Calmette-Gu6rin bacillus (BCG) to control cutaneous melanoma by intralesional injection has been demonstrated by Morton and co-workers [29] and confirmed by many other investigators. These studies and extensive animal experiments indicate that immunotherapy is most effective when the immunostimulating agent comes into close contact with the tumor. Rapp, Zbar, and their associates [44, 511 have shown that injecting BCG into a tumor growing in the flank of a guinea pig induces regression of regional lymph node metastases from that tumor and results in permanent cure. This treatment is more effective than giving the immunostimulating agent at a site distant from the growing tumor. Human immunotherapy trials have also demonstrated that direct injection of immunostimulants into the tumor gives rise to better systemic antitumor immunity and is capable of controlling microscopic amounts of disseminated disease, similar to the animal model [281. In many clinical situations, and always with surgical adjuvant therapy, the tumor is not available for direct injection. Therefore the use of tumor cells propagated in tissue culture, mixed with BCG and injected intradermally into patients, has been studied as an alternative method for immunotherapy used as a surgical adjuvant. Preliminary results from our laboratory indicate that this treatment is effective.
Active and Passive Immunotherapy Immunotherapy can be administered in an active or passive form, and active immunotherapy may be either specific or nonspecific. In the specific form, the patient’s immune mechanisms are directed against specific tumor antigens. The antigen used may be living or irradiated whole tumor cells, cell fragments, or cell-free tumor antigens. Active nonspecific immunotherapy serves as a nonspecific stimulus to the immune response. Immunological adjuvants such as BCG, Corynebacteriurn pauzium, or levamisole hydrochloride are nonspecific immune stimulators and can augment humoral as well as cellular immunity to tumor antigens as well as to other antigens [3, 38, 42, 471. Passive or adoptive immunotherapy involves
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the transfer to the cancer patient of immune factors from another host of the same or a different species who has been immunized against tumor-associated antigens. This transfer may be in the form of serum antibodies, immune lymphoid cells, or subcellular fractions of lymphoid cells such as transfer factor or immune ribonucleic acid (RNA) [30, 321. One particularly appealing method of passive immunotherapy entails the transfer of informational molecules that can arouse a specific immune response in the recipient’s own immune system. The two substances known to have this remarkable ability are Lawrence’s transfer factor and immune RNA [30,32]. Transfer factor is capable of transferring immunity to skin grafts, purified protein derivative (PPD), and a variety of other antigens and is able to repair immune defects in certain immunodeficiency diseases. It has not been used extensively for cancer immunotherapy but has been helpful in the treatment of some disseminated fungal and viral diseases. The investigation of transfer factor is somewhat hampered by the fact that it can be obtained only from human donors, and there are currently no animal models in which this therapy can be evaluated. Immune RNA, extracted from the lymphoid tissues of a xenogeneic host following immunization with tumors, can induce immunity in syngeneic recipients of tumor transplants t371. Immune RNA is highly advantageous because it can be produced by immunizing a host other than man. The use of heterologous immune RNA to induce tumor immunity has been quite successful in animal models and is currently undergoing early clinical trials [32, 371. Though transfer factor and immune RNA are being evaluated in several centers, to date no objective therapeutic benefit has been consistently observed. It must be emphasized that the studies are only Phase I trials, and the complete therapeutic potential of these modalities is still unknown. Both methods of immunotherapy have considerable promise because each bypasses many of the problems associated with other types of passive and adoptive immunotherapy such as HL-A incompatibility, serum sickness, and anaphylaxis, to name a few. Finally, it should be mentioned that immunotherapy has been demonstrated to be a use-
ful adjunct to chemotherapy. Israel [20, 211 has shown that nonspecific immunotherapeutic stimulation can increase the response rate to chemotherapy and the duration of the response, markedly diminish the side-effects of chemotherapy, and also allow for administration of greater amounts of chemotherapy.
Tumor-Specific Antigens Another important aspect of the rapidly growing field of tumor immunology is the definition and purification of tumor-associated antigens that are characteristic of certain neoplasms. The best known of these antigens are carcinoembryonic antigen and alpha-fetal protein [14, 361, which can be detected in the plasma of patients with certain types of neoplasms. The quantity of the circulating antigen is directly related to the total tumor burden. These and similar antigens in other neoplasms must be further developed if immunotherapy is to be used in a prophylactic manner following resection. Since in this setting the disease is subclinical and cannot be measured by clinical means, the ability to monitor tumor burden-and thereby response to surgical adjuvant immunotherapy-by measurement of circulating tumor antigens is extremely valuable. Attempts are being made to isolate and purify tumor antigens in a variety of neoplasms for this purpose. General Principles of lmmunotherapy Several important principles have been developed from experience in animal and human studies: It is clear that immunotherapy is effective
against only a limited amount of disease. Therefore it will be most effective in clinical situations in which the majority of tumor burden has been reduced surgically so that immunotherapy can be initiated when the tumor burden is minimal. Nonspecific immunostimulating agents are most effective when injected directly into the tumor or administered with tumor cells, and the most potent systemic immunity results when the nonspecific immune stimulator comes into direct contact with tumor antigens.
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3 . The level of immunocompetence is directly cancer was originally suggested by the studies of related to prognosis and stage of disease, and Krant and associates [241. Further studies have efforts at reversing immunodeficiency states shown that reactivity to DNCB is directly related are very important. to prognosis, stage of disease, and even resect4. Specific tumor immunity can be transferred ability [49, 501. Interestingly, the reactivity to the with cell-free products, such as transfer factor recall antigens was essentially the same in paand immune RNA, and can be used to recon- tients with lung cancer as in normal people. stitute immunodeficiency states. Wells and co-workers [49, 501 studied 75 lung 5. Immunotherapeutic maneuvers should be cancer patients and 25 patients with benign lung designed to augment cell-mediated immu- disease and confirmed that more than 96% of nity selectively, since in some tumor systems those with benign disease were capable of becomstimulation of humoral antibody may serve to ing sensitized to and reacting to DNCB. Only 52% of the patients with lung cancer could be enhance tumor growth. Invitro techniques can be used to monitor the sensitized to DNCB. In addition, they found that 6. patient’s response to therapy by quantitating 70% of the patients with lung cancer who the amount of circulating tumor antigen. reacted to DNCB had resectable disease compared with only 3 DNCB-negative patients. It is clear that immunotherapy can be highly They also showed that survival was superior in effective in animal systems and in certain patients who reacted to DNCB. Another inhuman neoplasms. It is therefore appropriate teresting observation was that DNCB reactivity that the use of immunotherapy be evaluated exwas more suppressed in patients with squatensively in patients with lung cancer. mous cell carcinoma than in patients with Immunocompetence of Lung Cancer Patients adenocarcinoma. In our own studies of more When compared to the survival of patients with than 100 patients with pulmonary carcinoma we most other neoplasms, the prognosis for lung found that no patients with Stage I11 (dissemicancer is very poor and suggests that there is nated) disease were capable of reacting to something unique about the cancer or the pa- DNCB; however, 50% of these patients did retient which allows for rapid progression of the spond to one of the recall antigens. We tested 33 disease. These observations have led inves- patients preoperatively with DNCB and found tigators to evaluate the immunocompetence of that reactivity to DNCB was closely related to patients with lung cancer by studying their resectability. We have seen only 2 DNCBdelayed cutaneous hypersensitivity to 2,4- positive patients whose tumor was unresectable dinitrochlorobenzene (DNCB) and to the so- and 1DNCB-negative patient who had resectable called recall antigens (PPD, mumps, Candida, disease. In our studies the response to recall Varidase). Skin testing with DNCB involves ap- antigens did not relate to resectability. plying this chemical to the skin and allowing the The fact that the majority of lung cancer papatient to become sensitized to it over a two- tients are capable of reacting to the standard week period. The patient is then challenged recall antigens in a manner similar to patients with a second, smaller dose of DNCB, and the with benign disease, while at the same time cutaneous reactivity to the antigen is quanti- being unable to become sensitized to DNCB, tated. Testing with DNCB evaluates the pa- suggests that the immunological defect in patient’s ability to process a new antigen and gen- tients with lung cancer most likely lies in the erate an immune response to it and therefore afferent limb of the immune mechanism. Certests the afferent and efferent limbs of the im- tainly, correction of this immunological defimune response. Skin testing with a recall anti- ciency should lead to improved survival. gen tests immunological memory. Since most Since it is well known that lung cancers elabopatients have been previously sensitized to one rate biologically active substances such as of these four agents, recall antigens test only the parathyroid hormone, adrenocorticotropic efferent limb of the immune response. hormone, and serotonin [351, and since these Immunodeficiency in patients with lung cancers are known to be associated with a
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number of intriguing paraneoplastic syndromes, it is not unreasonable to suspect that lung tumors could also elaborate immunoregulatory substances. Such a substance has been described by Glasgow and colleagues [13], who showed that a highly immunosuppressive immune regulatory alpha (IRA) globulin is present in the plasma of cancer patients and is closely correlated with the inability to respond to DNCB. Sample and co-workers [41] have reported that serum from patients with cancer inhibits lymphocyte function in vitro. Of the 9 patients they studied who had the immunosuppressive substance in their serum, 2 had bronchogenic carcinoma. It is therefore possible, and perhaps likely, that lung tumors elaborate immunosuppressive substances and that resection of the neoplasm may well be associated with an improvement in the immunodeficiency state. A variety of in vitro tests have also been used to demonstrate immunodeficiency in patients with lung cancer. The ability of lymphocytes from patients with lung cancer to respond by increased DNA synthesis in the presence of various mitogens and antigens has been evaluated. A number of investigators [7,15,161 have shown that by these criteria, patients with lung cancer are profoundly immunodepressed and that lymphocytes from cancer patients are far from normal in their ability to undergo deoxyribonucleic acid synthesis in the presence of immunological stimuli in vitro. This interesting immunological lymphocyte defect is being extensively evaluated, and immunotherapeutic substances that will reverse the immune paralysis are being sought. In summary, it is clear that patients with lung cancer are immunodepressed and that this directly affects their prognosis. Treatment thus should be directed toward reversing immunosuppression. Extirpation of the tumor may be an important step in this process since it may serve to improve immunocompetence.
have been demonstrated by a variety of techniques, and these same methods have recently been applied to the study of human lung tumor antigens. While these antigens have not been as extensively investigated as those of other tumors such as colon cancer, sarcoma, breast cancer, and melanoma, in the recent past a number of investigators have detected tumor-associated antigens in lung cancer [5, 18, 19, 27, 31,39,46, 49, 501. Wells and associates [49, 501 have described an antigen present on the membrane of lung tumors that is capable of eliciting specific delayed cutaneous hypersensitivity reactions. In these studies, 9 of 16 patients with lung cancer had delayed cutaneous hypersensitivity to a lung tumor membrane antigen, whereas only 1 reacted to a membrane antigen derived from normal lung tissue. These studies indicate that lung tumors have antigens on their surface which are different from normal lung antigens and which are capable of eliciting delayed cutaneous hypersensitivity or cellular immunity in some patients with lung cancer. Several in vitro assays have been used to demonstrate antigens in pulmonary carcinoma that are both unique to the tumor and capable of eliciting an immune response in the host. These studies-which include leukocyte immobilization in agarose [5], leukocyte adherence inhibition,* stimulated protein synthesis [431, colony inhibition [18], lymphocyte blastogenesis [271, and immunodiffusion [31]-have all confirmed the presence of specific tumor antigens on the surface of lung tumor cells. They have also shown that a common antigen occurs in all lung cancers regardless of histological type, though evidence exists, too, that there may be other antigens which are unique to lung tumors of the various histological types [19,31]. These in vitro studies have also confirmed that the host is capable of responding immunologically against these tumor antigens, which are not present in corresponding normal lung. The majority of these studies are quite recent, and data regarding in vitro reactivity to lung tumor antigens as Lung Tumor Antigens it relates to stage of disease and prognosis are In order for immunotherapy to be effective, the not yet available. However, it would not be surtumor must contain antigens which are unique prising to find demonstrable in vitro lymphoto it and against which the patient can generate an immune response. Tumor-associated antigens *MM Urist and EC Holmes, report in preparation.
255 Collective Review: Holmes: Immunology and Lung Cancer
cyte immunity in patients who have progressive clinical disease. Since these assays are performed in vitro (in the absence of the patient’s serum), certain humoral factors that suppress lymphocyte activity in vivo may be lacking; these could be nonspecific immunosuppressing factors such as IRA [13] or specific blocking factors such as those described by Hellstrom and co-workers [17]. The presence of these factors may explain why in vitro cellular immunity is frequently observed in patients who have progressive disease. One of the most promising and exciting aspects of the study of lung tumor antigens involves their purification and chemical characterization. When these antigens have been sufficiently purified, they can be used to develop highly sensitive serological tests, such as radioimmunoassay, with which one can detect small amounts of circulating tumor antigen in the plasma. One can then monitor the response to therapy in patients with subclinical disease: rising levels of these circulating tumor antigens indicate early recurrence and reflect the response to various therapeutic attempts to control the disease. Tumor cells contain a number of different antigens, many of which are shared by various neoplasms of different histological types. For example, an antigenic site on carcinoembryonic antigen is present in the sera of a high percentage of lung cancer patients. The magnitude of elevation of this antigenic determinant in the patient’s serum is directly related to extent of disease and could be used to monitor possible occult recurrences before they are clinically detectable [6, 261.
Possibilities for Immunotherapy of Lung Cancer Although lung cancers contain antigens against which the host can react immunologically, patients with lung tumors are frequently immunosuppressed and are not capable of initiating an adequate immune response. It seems reasonable, therefore, to attempt to augment the host immune response to these antigens and to try to reverse the immunodepression of lung cancer. Indeed, surgical extirpation alone may play a very important role in reversing the im-
munodeficiency state by removing a possible source of immunosuppressive substances. There is clinical evidence that some patients with lung cancer are capable of reacting against their tumors. A few reports have appeared of spontaneous tumor regression in patients with bronchogenic carcinoma, and in 1 instance the patient’s lymphocytes were found to be strongly cytotoxic against lung cancer cells [4]. An intriguing report from Ruckdeschel and his colleagues [40] indicated improved survival in patients with resectable lung cancer who developed postoperative empyema compared with similar patients who did not. The difference in survival between the two populations was highly statistically significant. This experiment of nature suggests that perhaps surgical extirpation along with a potent nonspecific immunological stimulant to the regional lymph nodes such as chronic empyema has a beneficial effect on survival in patients with lung cancer. Animal experiments support these clinical impressions, indicating that systemic immunotherapy is capable of curtailing tumor growth within the pulmonary parenchyma. Baldwin and Pimm [l] evaluated the immunotherapy of pleural and pulmonary neoplasms in animal systems and found that intravenous BCG can prevent pulmonary metastases following intravenous injection of tumor cells. This effect was noted when BCG was given as late as seven days after the injection of tumor cells. Spontaneous pulmonary metastases following the removal of a transplanted neoplasm are also suppressed by intravenous administration of BCG. In addition, spontaneous metastases by a primary hepatoma have been prevented by intravenous injection of BCG [21. And finally, Baldwin and Pimm [33] have shown that intrapleurally injected BCG is capable of controlling actively growing pleural tumors; BCG injected intravenously, subcutaneously, or intraperitoneally had no effect on the growth of these tumors. As a result of these studies, clinical trials with intrapleural BCG are now being carried out in Belfast, Ireland, in patients with mesothelioma. While the animal immunotherapeutic experiments have not been directed toward a primary pulmonary neoplasm, BCG and C. parvurn do concentrate in the pul-
256 The Annals of Thoracic Surgery Vol 21 No 3 March 1976
monary parenchyma and are capable of inducing an antitumor response within it following their intravenous injection. The immunotherapy of human lung cancer can take one of several forms previously mentioned. To date, most ongoing trials involve active nonspecific immunotherapy. The results of immunotherapy for malignant melanoma following wide excision and removal of regional lymph node metastases is very encouraging for the prospect of effective immunotherapy of lung cancer, since these studies are based on the principle of surgical reduction of the tumor burden and use of immunotherapy prophylactically before clinical recurrence has developed [28]. Nonspecific immune-stimulating agents that are currently being evaluated in patients with lung cancer are BCG, C . parvum, and levamisole. All three have been shown to be effective immune stimulants in extensive animal investigations, and they have potent immunostimulating effects in patients [3, 28, 38, 42, 471. All these agents have been evaluated in Phase I trials; the toxicity has been carefully evaluated, and acceptable nontoxic doses and routes of administration have been determined. BCG is an attenuated, viable bovine tubercle bacillus and is usually supplied in a lyophilized state; the lyophilized material is reconstituted and administered to patients by intradermal injection. Corynebacterium parvum is a formalin-treated, killed bacterium that is usually administered by the intravenous route. These two agents are usually administered once weekly on an outpatient basis. Levamisole has a distinct advantage in that it is not an organism but a chemical. It is given orally in the form of a pill and is usually taken daily for three days every one or two weeks. Several ongoing clinical trials are being conducted in the United States and Europe to evaluate these three agents as surgical adjuvants following pulmonary resection. Some of these studies are well into their second year, and it is hoped that clinical data will be available in the near future. Active specific immunotherapy for lung cancer has lagged behind active nonspecific immunotherapy because lung cancer cells are difficult to propagate in tissue culture, making a constant and reliable source of tumor antigens
difficult to supply. However, with the development of soluble lung tumor antigens and improved tissue culture techniques, it is likely that active specific immunotherapy for lung cancer will become possible in the very near future. In addition, cell-free materials such as immune RNA can be developed and used in patients with lung cancer. However, trials with immune RNA and other specific active immunotherapeutic agents have just recently been initiated, and only a few studies evaluating immunotherapy in patients with lung cancer have been completed. Some investigators have administered BCG to patients with bronchogenic carcinoma and have observed tumor regression in up to 28%. In addition, survival in these patients was superior to that in controls [221. BCG has been combined with chemotherapy in patients who have lung cancer with a decidedly beneficial effect [48]. Finally, Takita and Brugarolas [45] treated 5 patients who had locally advanced bronchogenic carcinoma with an autologous tumor vaccine following incomplete surgical resection and considered this active specific immunotherapy responsible for improved survival in the treated group: 3 of 5 patients treated with the tumor vaccine were alive at eighteen months, whereas all 6 control patients had died by that time. While the immunotherapy of lung cancer is certainly in its infancy and reliable clinical results have not yet been reported, sufficient information is available from animal models, immunological studies in patients with lung cancer, and immunotherapy trials in patients with other neoplasms to suggest strongly that immunotherapy will have a role in the treatment of patients with lung cancer.
References 1. Baldwin RW, Pimm MV: BCG immunotherapy of pulmonary growths from intravenously transferred rat tumor cells. Br J Cancer 27:48, 1973 2. Baldwin RW, Pimm MV: BCG suppression of pulmonary metastases from primary rat hepatoma. Br J Cancer 30:473, 1974 3. Bast RC, Zbar B, Borsos T, et al: BCG and cancer. N Engl J Med 290:1413, 1974 4. Bell JW: Possible immune factors in spontaneous regression of bronchogenic carcinoma. Am J Surg 120:804, 1970 5 . Boddie AW, Holmes EC, Roth JA, et al: Detection
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of cell mediated immunity to soluble human lung cancer antigens. Int J Cancer 15:823, 1975 6. Broder LE, Walkes TP, Primack A, et al: Biologic markers in the evaluation of disease status of patients with advanced bronchogenic carcinoma. Proc Am Assoc Cancer Res 16:223, 1975 7. Brugarolas A, Han T, Takita H, et al: Immunologic assays in lung cancer. NY State J Med 73:747,1973 8. Brunner KW, Marthaler TH, Miller W: Effects of long-term adjuvant chemotherapy with cyclophosphamide for radically resected bronchogenic carcinoma. Cancer Chemother Rep 4:125, 1973 9. Ducos J, Migueres J, Colombies P: Lymphocyte response to PHA in patients with lung cancer. Lancet 1:1111, 1970 10. Eilber FR, Morton DL: Impaired immunologic reactivity and recurrence following cancer surgery. Cancer 25:362, 1970 11. Eilber FR, Nizze JA, Morton DL: Sequential evaluation of general immune competence in cancer patients: correlation with clinical cancer. Cancer 35:660, 1975 12. Fisher BR, Barbone P, Economou SC, et al: Phenylalanine mustard in the management of primary breast cancer. N Engl J Med 292:117, 1975 13. Glasgow AH, Nimberg RB, Menzoian JO: Association of anergy with an immunosuppressive peptide fraction in the serum of patients with cancer. N Engl J Med 291:1263, 1974 14. Gold P, Friedman SO: Specific carcinoembryonic antigens of the human digestive system. J Exp Med 122:467, 1965 15. Gross RL, Latty A, Williams E, et al: Abnormal spontaneous rosette formation and rosette inhibition in lung cancer. N Engl J Med 292:339, 1975 16. Han T, Takita H: Impaired lymphocyte response to allogeneic cultured lymphoid cells in patients with lung cancer. N Engl J Med 286:605, 1972 17. Hellstrom I, Hellstrom KE, Pierce GE, et al: Cellular and humoral immunity to different types of human neoplasms. Nature (London) 220:1352, 1968 18. Hellstrom I, Hellstrom KE, Sjogren HO, et al: Demonstration of cell mediated immunity to human neoplasms of various histological types. Int J Cancer 7:1, 1971 19. Hollinshead AC, Steward THM, Herberman RB: Delayed hypersensitivity reactions to soluble membrane antigens of human malignant lung cells. J Nat Cancer Inst 52:327, 1974 20. Israel L: Preliminary results of non-specific immunotherapy for lung cancer. Cancer Chemother Rep 4:283, 1973 21. Israel L, Edelstein RL: Non-specific immunostimulation with Corynebacteriurn parvum in human cancer, Immunological Aspects of Neoplasia. From the M. D. Anderson Hospital and
Tumor Institute. Baltimore, Williams & Wilkins, 1974 22. Khadzhiev S: Treatment of bronchial cancer patients with a water saline extract of BCG. Vope Onkol 17:51, 1971 23. Klein E: Hypersensitivity reactions at tumor sites. Cancer Res 27:2351, 1969 24. Krant JK, Manskopf G, Bandrup C, et al: Immunologic alterations in bronchogenic cancer. Cancer 21:573, 1968 25. Lee YN: Prognostic factors in surgical treatment of bronchogenic carcinoma. Surg Gynecol Obstet 135:961, 1972 26. LoGerfo P, Herter FP, Braun J, et al: Tumorassociated antigen with pulmonary neoplasms. Ann Surg 175:495, 1972 27. Mavligit GM, Gutterman JU, McBride CM, et al: Cell-mediated immunity to human solid tumors: in vitro detection by lymphocyte blastogenic responses to a cell-associated and solubilized tumor antigen. Nat Cancer Inst Monogr 37:167, 1973 28. Morton DL, Eilber FR, Holmes EC, et al: BCG immunotherapy of malignant melanoma. Ann Surg 180:635, 1974 29. Morton DL, Holmes EC, Eilber FR, et al: Immunological aspects of neoplasia: a rational basis for immunotherapy. Ann Intern Med 74:587,1971 30. Neidhart JA, LoBuglio AF: Transfer factor therapy of malignancy. Semin Oncol 1:379, 1974 31. Nordquist RE: Specific antigens in human alveolar cell carcinoma. Cancer Res 33:1790, 1973 32. Pilch YH, DeKernion J: Immunotherapy of cancer with immune RNA: current status. Semin Oncol 1:387, 1974 33. Pimm MV, Baldwin RW: BCG therapy of pleural and peritoneal growth of transplanted rat tumors. Int J Cancer (in press) 34. Prehn RT, Main JM: Immunity to methylcholanthrene-induced sarcomas. J Nat Cancer Inst 18:769, 1957 35. Primack A: The production of markers by bronchogenic carcinoma: a review. Semin Oncol 1:235, 1974 36. Purves LR, Bershon I, Geddes EW: Serum alpha fetal protein and primary cancer of the liver in man. Cancer 25:261, 1970 37. Ramming KP, Pilch YH: Mediation of immunity to tumor isografts in mice by heterologous ribonucleic acid. Science 168:492, 1970 38. Renoux G, Renoux M: Levamisole inhibits and cures a solid malignant tumor and its pulmonary metastases in mice. Nature New Biol 240:217, 1972 39. Roth JA, Holmes EC, Boddie AW, et al: Lymphocyte responses of lung cancer patients to tumorassociated antigen measured by leucine-incorporation. J Thorac Cardiovasc Surg 70:613, 1975 40. Ruckdeschel JC, Codish SD, Stranahan A, et al:
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