Cancer TreatmentReviews (1975) 2, 295-322

C y c l o p h o s p h a m i d e in solid tumors Stephen K. Carter

Deputy Director, Division of Cancer Treatment, National Cancer Institute, Bethesda, Md 20014, U.S.A. and Robert B. Livingston M.D. Anderson Hospital and Tumor Institute Houston, Texas, U.S.A.

Introduction The alkylating agents are the oldest group of cytoxic chemicals in the armamentarium of the medical oncologist. In fact, the discovery of the anticancer effect of one of these agents, nitrogen mustard, ushered in the modern era of cytotoxic cancer chemotherapy shortly after World War II. There soon followed a wide range of compounds with the same basic mechanism of action designed in the hope of improving the therapeutic index of this active class of compounds. Cyclophosphamide (Cytoxan, Endoxan) is the most widely used of these subsequently developed analogues. Clyclophosphamide (CTX) was first synthesized by Arnold, Bourseaux and Brock (7, 8, 19, 22). The rationale of the synthesis was to introduce a chemical group to transform the active chemical group into an inert transport substance which would be reconverted into the active form at the site of therapeutic action in the body. Earlier, Friedman and Seligman (57) had combined an active bis-(/3-chloroethyl) amino group with phosphoric acid but the resulting compounds were inactive. Arnold and his group allowed bis-~-chloroethyl-phosphamide-dichloride to react with alkanolamines and obtained Cyclic bis-(~-chloroethyl)-phosphamide esters with two phosphamide bonds and one ester bond. The result was the synthesis of the cyclic propanol amide ester of bis-(/3chloroethyl)-phosphamide, which is CTX. Originally, since tumor cells show elevated phosphatase and phosphoramidase activity, the Asta-Werke group felt that the alkylating moiety of CTX would be liberated by tumor cells through enzymatic cleavage from the inactive N-phosphorylated pre295

296

S.K. GARTER AND R. B. LIVINGSTON

cursors to a higher degree than by normal cells. The process involved turned out to be more complex than had been expected on hypothetical grounds. Brock and Hohorst (20, 21) could show that GTX is activated by the microsomal drug metabolizing system of the liver, with active metabolites reaching their target sites through the systemic circulation. Widespread and exhaustive studies to elucidate the exact mechanism of activation and isolate the active metabolltes have been made during the approximately 15 years since the drugwas first shown to be active. The current view of the CTX activation is that the liver microsomal mixed-function oxidase system converts the drug to 4hydroxycyclophosphamide, which is in equilibrium with its aeyclic taut0meric form, aldophosphamide (34, 38, 39). Further oxidation of aldophosphamide, possibly through the mediation of liver aldehyde oxidase and other aldehyde-metabolizing enzymes, results in the formation of carboxyphosphamide. Another pathway for the disposition of 4-hydroxycyclophosphamide is dehydrogenation to 4-ketocyclophosphamide, another end product of GTX metabolism. Both carboxyphosphamide and 4-ketocyclophosphamide have been tested and neither has significant biological activity. Dose schedules

GTX has been in widespread clinical trial since 1960 and a broad range of dose schedules have been evaluated. The availability of both oral and parenteral formulations has even further increased the complexity of the various schedules tested. The schedules for which significant data exist are: (1) High dose intermittent--1 to 1.5 g/m2 (30-50 mg/kg) as a single rapid IV infusion; repeated as soon as the WBG returns toward normal (usually 21 days). (2) Loading course with or without maintenance--30 to 40 mg/kg over 5-10 days, either IV or PO (usually IV) ; can be followed by PO maintenance. (3) Chronic daily administration--2 to 3 mg/kg/d IV or PO until toxicity; PO maintenance as tolerated. (4) Weekly--I 5 mg/kg/wk, usually IV. Extensive observations have been made in the most responsive tumors using most, if not all, of these schedules. However, the paucity of data from controlled comparative trials makes a definitive statement on the superiority of any single schedule very tenuous. As a matter of fact, analysis of all the data leads to the impression that in clinical use the drug is not very schedule sensitive, in contrast to preclinical experience in the mouse leukemia L1210 model system. This question will be explored further as the data for individual diseases are analyzed. Toxlclty Like the other alkylating agents, the major toxic effect of CTX is on the bone marrow but its spectrum of toxicity is a bit wider. GTX has been claimed to be superior to other alkylating agents because of its so-called platelet sparing effect, i.e. a greater effect on the peripheral white blood cells than on platelets. This dissociation has been noted by many investigators (14, 36, 53, 115, 124)but one dissenting view by Jacobs et at. (77) reported the platelet sparing effect of the drugwas clinically insignificant compared to th~at of nitrogen mustard in the treatment of malignant lymphomas.

CYCLOPI-IOSPHAMIDE IN SOLID TUMORS

297

Pegg (96) made a detailed study of the marrow effect and concluded that C T X doses that reduce the white blood count to 1000/ram 3 actually stop production ofgranulocytes and platelets but the speed of recovery is exceptionally rapid in comparison with other alkylating agents. Since the platelet has an average life span of 8 days, compared to 4 days for the granulocyte, platelet count does not drop as low as the white blood count. The studies of bone marrow performed by DeWys (48) support this theory but observations by Coggins et al. (36) and Wall and Conrad (124) are contradictory to some degree. They reported that C T X produced suppression of granulopoiesis but not diminished bone marrow megakarocyte activity. Despite these differences of opinion on the marrow effect, most clinicians agree that one of the major advantages of C T X is its diminished platelet toxicity. The nadir of marrow suppression occurs early in nearly all studies. Kontras and Newton (84), using 5-10 mg/kg/d in children, noted a drop in white blood count within 5 to 7 days after starting therapy. Stoll and Matar (I 17) found that maximum white blood count depression occurred within 7 to 13 days of administration of a single large dose, while Solomon et al. (115) noted the peak drop in 9 days and Thurman et al. (120) in 8 days. The great majority of investigators reported a return to normal blood counts by I0 days after the maximum drop (5, 9, 115, 120) and many patients recovered sooner. Bergsagel et al. (15), who used 40-50 mg/kg IV as a single dose, found it safe to again administer the same dose after the white blood count returned to 75% of its original level. There is general agreement that patients having marrow depression due to previous therapy should receive smaller doses, which is true for most, if not all, marrow toxic agents. Kontras and Newton (84) observed that neuroblastoma patients with marrow metastases experienced greater toxic effects than those without such involvement. Bergsagel and Levin (14) found that patients with pre-existing liver damage were also more sensitive to CTX. Bladder toxicity is a side effect unique to C T X among the alkylating agents and caused by contact of its irritating metabolites with the bladder mucosa (97). The first sign of bladder damage is urinary frequency, followed by dysuria and, finally, by hematuria. General experience has shown that a high fluid intake can prevent cystitis in most patients (80, 83). In children who received long-term C T X there have been reports of significant bladder scarring observed at autopsy (80, 104, 119). Alopecia is fairly common and occurs most frequently with high dose IV regimens. Nausea and vomiting often occur, especially with IV daily doses above 4 mg/kg. The onset is at least six hours after drug administration and the symptoms last for about four hours. Slightly higher doses are tolerated better when given IV rather than orally. There have been isolated reports of liver damage by C T X (10) but liver toxicity is not among the major hazards of the drug. This is interesting in view of the activation of C T X by the liver. The resistance of the liver to the toxic effects of the drug m a y result from the presence of aldehyde-oxidizing enzymes capable of rapidly cleaving aldophosphamide (49). These enzymes are present at low or undetectable levels at most other sites including the hematopoietic tissues. Increasing use of long-term C T X is revealing newer types of toxicity, prominently including sterility and testicular atrophy in males (52). Azoospermia or oligospermia have been observed, with no spermatogenesis being detectable upon testicular biopsy. In females, amenorrhea is frequently seen in prolonged therapy and drug-induced ovarian fibrosis has been reported. Teratogenic effects secondary to C T X have been

298

S. K: C A R T E R AND R. B. LIVINGSTON

demonstrated in experimental animals and similar effects, such as absent toes a n d coronary artery abnormalities, have been described in infants of mothers with Hodgkin's disease who received the drug during the first trimester of pregnancy. These effects may be dose-related since there are no reports of ill effects with low doses during the first trimester (35). Another recently described side effect is impairment of water excretion (46) which is frequently seen at high dose levels (>50 mg/kg). This is an important observation in view of the vigorous hydration to which CTX-treated patients are frequently subjected. This toxic effect results in hyponatremia, weight gain and inappropriately concentrated urine during and after C T X infusion. Other less commonly reported toxicities include temperature rise (53) after IV doses, skin hyperpigmentation (120) and mueosal ulcerations (1).

CHnlcal activity C T X has shown activity against an extremely wide range of tumor types. One means of approaching analysis of this massive data base is a disease-oriented survey. In this technique the single agent data for each tumor type will be initiaIly reviewed, followed by evaluations of combination chemotherapy. Where applicable, combined modality (32) trials involving the drug will be described. Breast cancer Single agent chemotherapy. C T X has been the most extensively studied alkylating agent i n breast cancer and is generally acknowledged to be the alkylating agent of choice. Since it is available in both parenteral and oral formulations, it has been used on a wide variety of dosage schedules. This is in contrast to xts counterparts ~nitrogen mustard thio-TEPA, and chlorambucil) which have all been administered on schedules almost totally consistent for each given agent. The data reviewed by Carter (30) for chronic daily administration of C T X show an overall response rate of 35 % (371106). The response rates i n individual studies range from a low of 10% (124) to as much as 62% (63), Full discussion of the reasons for these differences is outside the scope of this review but obviously patient selection, intensity of treatment, definition of response and definition of the study population are among the most important variables leading to these differences. The loading course IV schedule, usually followed by oral daily maintenance, has been the most commonly used schedule with 395 patients reported (30). The overall response rate of 35 % (137/395)is identical to that obtained with chronic daily administration. Data for patients treated on intermittent schedules has been too scanty to draw conclusions (30). However, it would be interesting to see additional data on the high single dose regimen ofBergsagel et al. (15) that showed high activity. The overall response rate for C T X in 529 patients is 34% (1821529) (30). Only a f e w reports have attempted to correlate the C T X response rate with pre-therapeutic variables, such as previous therapy, menopausal status, predominant site of disease and disease-free interval (18, 94, 102). Concerning the correlation between response to C T X and the results of previous endocrine therapy, the responsiveness of patients treated with C T X is essentially the same

CYCLOPHOSPHAMIDE IN SOLID TUMORS

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regardless of whether they did or did not respond to endocrine therapy (30, 94, 102) Nemoto and Dao specifically studied response to adrenalectomy and reported no difference in response to subsequent C T X treatment (94). When one correlates menopausal status and C T X response, it appears that the best overall response (38%) is seen in women who are less than a year post-menopausal (30). This rate decreases to only 18% in women 5 to 10 years post-menopausal and then rises again. Nemoto and Dao (94) interpret the higher response rate in patients less than a year after menopause as indicating that tumors not responsive to castration may be more apt to respond to chemotherapy. Unfortunately, no study specifically considers this variable, although Ravdin and Eisman (102) allude to it especially for 5-fluorouracil therapy. When the site of the dominant lesion and its relationship to C T X response is evaluated (30), there is a tendency for a higher response rate in soft tissue lesions (43 %) compared to osseous (24%) or visceral lesions (28%). Nemoto and Dao (94) break down visceral lesions in greater detail. In their experience, patients having hepatic metastasis with jaundice had the least response to the drug (0]10) followed by patients with brain metastasis (I/17). The last variable examined is the disease-free interval and its correlation with response. A tendency is seen for a higher response rate in patients with a short disease-free (5 yr

31% (20]65) 32% (13]41) 13 % (3]24)

As can be seen, they also observed a tendency for lower response in patients with a long disease-free interval, but their break is at 5 rather than 2 years. Clearly, more data analyzed in greater detail are needed on this important point. Combination chemotherapy. Since C T X has significant activity in breast cancer it has been included in nearly all of the major combination drug regimens developed to treat advanced disease patients. Greenspan (66, 67) was one of the first investigators to successfully exploit combination chemotherapy in breast cancer and reported the results of two regimens that date back as far as 1963. With a 5-drug combination involving three cytotoxic compounds (including CTX) and two hormonal compounds, he achieved an 81% response rate in 73 cases. In 1969, at the meeting of the American Association for Cancer Research, Dr Richard Cooper (40) of the Buffalo Medical Group presented the results of a 5-drug combination consisting of the following; 5-Fluorouraeil (5-FU) Methotrexate (MTX) Vincristine (VCR) CTX Prednisone

12 mg]kg/d x 4, then 500 mg/wk IV 25-50 mg/wk IV 0.035 mg/kg/wk IV 2.5 mg/kg/d PO 0.75 mg]kg/d PO

300

S.K. CARTER AND R. B. LIVINGSTON

Table 1. Therapeutic reghnens evaluated by co-operative groups on the basis of the "Cooper

Group

Regimen 1

Regimen 2

Acute Leukemia Group B 4#6982

1. 2. 3. 4. 5.

5-FU 12 mg/kg/wk IV MTX 0.75 mg/kg/wk IV} x 8 VCR 25 pg/kg/wk } Cytoxan 2 mg/kg/d PO Prednisone 0.75 mg/kg/d PO x 2 I, then taper

Eastern Co-operative Oncology Group # 0971

1. 5-FU 600 mg/m~ d 1 and 8 2. MTX 60 mg/m2 d 1 and 8 3. Cytoxan 100 mg/m2/d • 14 PO, cycles repeated at 28-day intervals

I. Phenylalanine mustard, 6 mg/m2/d x 5 PO every 6 wks

Central Oncology Group # 7500

1. 2. 3. 4. 5.

5-FU 500 mg/wk IV MTX 25 mg/wk IV VCR 1 mg/wk IV Cytoxan 100 mg/d PO Prednisone 45 mg/d x 14 then taper

1. 2. 3. 4.

5-FU MTX ~ as in Regimen 1 Cytoxan [ Prednisone)

Southeastern Cancer Study Group # 339

1. 2. 3. 4; 5.

5-FU 400 mg/ma/wk IVl MTX 20 mg/m2/wk PO } x 8 VCR 1 mg/m2/wk IV / Cytoxan 100 mg/m2/d PO Prednisone 45 mg/d and taper

1. 2. 3. 4. 5,

5-FU 400 mg]m2 d 0 and 7 MTX 30 mg/m2 d 0 and 7 VCR 1 mg/m2 d 0 and 7 Cytoxan 400 mg]m2 d 0 IV Prednisone 20 mg q. i. d, x 7

I. 5-FU

2. VCR } as in Regimen 1 3. Prednisone /

vs

5-FU 600 mg/mZ/wk x 8 ~progressive disease MTX 20 mg/m2 twice weekly PO

Western CoZoperative Group # 115

prog. dis.

VCR I mg/m2/wk ~'progressive disease Cytoxan 100 mg/m2/d

>

I. 2. 3. 4.

5-FU 15 mg/kg IV every 2 wk MTX 0.5 mg[kg W every 2 wk Cytoxan 2 mg/kg/d PO Prednisone 0.5 mg/kg/d x 14, taper 5. Triiodothyronine 50 pg/d

Sequential use of 1. 5-FU 15 mg/kg/wk 2. Cytoxan 2mg/kg/d PO 3. Prednisone + Triiodothryonine 4. MTX 0.5 mg/kg/wk

Southwestern Group 4#450

1. 2. 3. 4. 5.

5-FU 300 mg/m2/wk MTX 15mg/m2/wk ] x 8 VCR 0.625 mg/m2/wkl Cytoxan 60 mg/m2/d Prednisone 30 mg]m2/d x 14, taper

1. 2, 3. 4. 5.

5-FU 180 mg/m2/d • 5 M T X 4 mg/m2/d x 5 Cytoxan 120 mg/m2/d • 5 VCR 0.625 mg/m2 d 1 and 5 Prednisone 40 mg/m2/d • 5 Repeat courses every 28 d

V$

New Agent (Adrlamycin 60 mg/m2 every 3 wks)

C o o p e r r e p o r t e d a 9 0 % c o m p l e t e remission rate in 60 h o r m o n e - r e s i s t a n t patients w i t h f a r - a d v a n c e d breast cancer. T h i s study deeply impressed the o n c o l o g y c o m m u n i t y a n d six c o - o p e r a t i v e groups sponsored by the N a t i o n a l C a n c e r I n st i t u t e sought to follow it u p in controlled evaluations. T h e t h e r a p e u t i c regimens e v a l u a t e d by each g r o u p ( T a b l e 1) c a n b e s u m m a r i z e d as follows:

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301

(1) Two groups compared the "Cooper regimen" with the same regimen minus one or two drugs. The Central Oncology Group (COG) removed VCR while Acute Leukemia Group B deleted CTX and MTX. (2) The Southeastern Cancer Study Group (SEG) and the Southwestern Group (SWG) compared the Cooper regimen, which is continuous drug administration, to an intermittent dose schedule of the five drugs. (3) The Western Cooperative Group (WCG) modified the Cooper regimen by removing VCR and substituting triiodothyronine, and compared this to sequential use of single agents. (4) Two groups compared the Cooper regimen to a single agent. The SEG made the comparison with sequential single agents beginning with 5-FU and the SWG compared the Cooper regimen to adriamycin. (5) The Eastern Cooperative Oncology Group (ECOG) removed VCR and prednisone, administering the remaining three drugs on an intermittent schedule and comparing it with phenylalanine mustard alone. Other investigators have experienced variable success in attempting to reproduce Cooper's data. A review of the published literature shows 9 series (Table 2) with response rates ranging from 29% to 70% and an overall rate of 50% in 348 cases, It must be emphasized that almost every series used some modification of Cooper's original dose schedule for the 5 drugs and that patient selection variables, intensity of treatment and data reporting techniques all contribute to the wide range of reported results. In general, the follow-up to Cooper's original report has been somewhat disappointing and no one has reproduced his 90% complete response rate. Two major co-operative groups with large series have noted response rates over 60% (mostly partial regressions) that appear greater than could be expected with single agents. Other groups have reported less impressive results and almost all would agree that the Cooper 5-drug combination is still a long way from exploting the optimum therapeutic potential of the compounds utilized. Three groups have studied the Cooper regimen without prednisone (Table 3). The results appear to be at least comparable, with an overall 57% response reported in 129 cases from the 3 series. While this would make it appear that prednisone has little to add in the original combination, such a conclusion must await a controlled comparison. Table 2. Treatment of advanced breast carcinoma by 5-drug chemotherapy derived f r o m the Cooper regimen

Investigators Lokichand Skarin (91) Ramirez (101) Leoneand Rege (88) Stott et al. (118) Vaughn et al. (123) Davis et al. (42) Dorsk et al. (50) Lemkinand Dollinger(87) Smalleyet al. (112) Totals

Number of patients evaluable

Numberof responses

%

10 50 81 10 46 74 20 20 37

7 34 51 5 20 31 8 6 11

70 68 63 50 43.5 42 40 30 29

348

173

50

response

S. K. CARTER AND R. B. LIVINGSTON

302

Table 3. Four-drug combination chemotherapy for advanced breast cancer t

Investigators Ramirez (100) DeLena et al. (47) Hanham et al. (70) Totals

Number of patients evaluable

Number of responses

% response

60 55 14

34 25 14

57 45 100

129

73

57

J"Cyclophosphamide,vincristine, methotrexate, 5-FU.

Three-drug combinations involving C T X have also been studied, The Mayo Clinic observed nearly a 50% response rate for 5-FU, C T X and prednisone (2). The Eastern Cooperative Ontology Group has seen impressive results with a combination of CTX, 5-FU and M T X (29). The more recent combination approaches involve C T X with adriamycin, the new antitumor antibiotic that may be the most active single agent in advanced breast cancer (16), At the NCI a newly devised 3-drug combination (CAF) consists of: Adriamycin CTX 5-FU

30 mg/m 2 days 1 and 8 I V 100 mg/m2/d x 14 P O 400 mg/m 2 days 1 and 8 PO

Each cycle is repeated every 28 days. This is being compared to a regimen (CMF) in which adriamycin is replaced by M T X at a dose of 40 mg/m 2 IV on days I-8 (28). Five of 8 patients have responded to CAF, compared to 4[ I 0 on CMF. This encouraging study, which suggests that adriamycin can be successfully integrated into a combination regimen, is continuing to accrue patients. A regimen, termed FAC, utilizing the same 3 drugs has also been developed at M. D. Anderson Hospital (I 7). The drugs are administered on a 21-day course as follows: Adriamycin CTX 5-FU

50 mg/m 2 day 1 IV 500 mg/m 2 day 1 IV 500 mg/m 2 days 1 and 8 IV

Twenty-five patients have been treated on this regimen with 3 complete and 15 partial remissions being observed for a 72% response rate. Among 13 patients completing 3 courses, there were 3 complete and 8 partial responses for an overall response rate of 84%. This pilot study, which had significant but acceptable toxicity, reveals major efficacy in metastatic breast cancer and will be further evaluated in a cooperative group study. Salmon and Jones (106) have developed a 2-drug combination of adriamycin (40 mg/m 2 day I) and C T X (200 mg/m 2 PO days 3-6) with courses repeated every 21 days, They have treated 26 consecutive patients with advanced breast cancer and treatment was well tolerated with no serious myelosuppression. O f 23 evaluable cases, 19 received an adequate trial (2 courses) and 16 of these showed excellent responses with >50% tumor regression; the ratios of responders/evaluable trials was 16/23 (70%) and responders/adequate trials 16/19 (84%). Only one responder has relapsed to date with a remission duration of 3 months.

CYCLOPHOSPHAMIDE IN SOLID TUMORS

303

Thus, three combinations including adriamycin + C T X either alone or in further combination with 5-FU have shown high activity in breast cancer and further studies are being vigorously pursued. It is clear that combinations involving C T X can give impressive response rates, although in every case they appear to be less than the additive response expected for optimal use of each component agent. Much work still remains to be done in elucidating the optimum combinations and sequences of drug administration. At this point no individual drug combination can be recommended as optimal. Despite this, the cell kill potential of combinations as evidenced by remission induction figures does appear to be higher and makes this approach highly attractive for use in combined modality regimens. Combinedmodalities. Since chemotherapy and hormonal therapy do not have overlapping toxicity and probably work through different mechanisms of action, a combination of the two modalities would seem an attractive concept and various studies are currently exploring this approach. In pre-menopausal females with recurrent tumor, remission rates ranging from 20% (121) to 40% (82) have been reported for bilateral ovariectomy. Combination chemotherapy, which is generally used after ovariectomy and even other therapies, gives response rates which appear to be superior, or at least, no worse. It would be interesting to speculate on the results of a controlled trial comparing ovariectomy and chemotherapy but this is not likely to be performed. However, several studies are underway which compare ovariectomy alone with this procedure plus chemotherapy (Table 4). T h e Acute Leukemia Group B and Mayo Clinic studies will test the possibility that chemotherapy given immediately after ovariectomy might increase the response rate, response duration, and survival over that achieved with ovariectomy alone. T h e NCI study will compare the effect of chemotherapy on the length of tumor response in patients who either respond to ovariectomy or show no change at 12 weeks. All patients in the NGI study will initially undergo ovariectomy. Patients who show evidence of progressive disease within 12 weeks will be removed from the study. Patients with either an objective response or no change post-ovarietomy will be randomized Table 4. Ovarlectomy + chemotherapy involving cyelophosplmnxide studies for treatment of metastatic or recurrent inoperable breast carcinoma currently supported by the National Cancer Institute

Institution

Arm 1

Arm 2

Arm 3

Acute Leukemia Group B Ovariectomy alone (ProtocolNo. 7382)

Ovariectomy + Cyclophosphamide Cooper regimen (15 mg/kg IV 2x weekly beginning beginning within within 14 days after ovariectomy 14 days after ovariectomy

Mayo Clinic

Ovariectomy alone

Ovariectomy + 5-FU (8 mg/kg/d • 5) Cyclophosphamide (4 mg/kg/d x 5) Prednisone (30 mg/d x 7) Then taper, coursesgiven q 5 wk

NCI, Bethesda

Ovariectomy alone

Ovariectomy + Cyclophosphamide - (100 mg/m2/d x 14) 5-FU (600 mg/m2 dl-8) Methotrexate (q-0mg/m2 d I-8) Beginning 8-I 2 wk postovariectomy in patients with response or no change status; repeated q 29 days

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to receive either no further therapy or a combination of CTX, MTX and 5-FU. When patients randomized to no further therapy relapse they will receive the combination regimen. No data are presently available from any of these studies. The use of CTX in a surgical adjuvant situation dates from the report of NissenMeyer (95) of the Scandinavian Adjuvant Chemotherapy Study Group. In this trial, patients received CTX (30 mg/kg I V ) o v e r a 6-day period starting with the day of surgery. They have consistently reported a diminished recurrence rate and survival gain which is statistically significant for the treated group. Currently the N C I is sponsoring several surgical adjuvant trials for breast cancer patients who have positive nodes after mastectomy, using prolonged chemotherapy to eradicate established metastatic loci (Table 5). Hopefully, in the next few years we will have some knowledge about the validity of this approach.

Bronchogenic carcinoma Single agent chemotherapy. CTX has been extensively studied as a slngle agent against bronchogenic carcinoma. Selawry (108) surveyed both the English language and selected foreign literature and reported an overall objective response rate of 20% in 1513 patients. Response rates in the individual studies ranged from 0 to 63%, which is not surprising in view of the difficulties in measuring objective response in lung cancer and the vagaries of patient selection as related to cell type, performance status and the influence of prior therapy. A selected, more detailed review of the English language literature also reveals a wide range of responsiveness, with a somewhat higher overall response rate of 33% in 533 cases (Table 6). Selawry's presentation of his data by cell type (Table 7) shows an expected slightly higher activity in the more responsive small cell type and comparable response in other cell types (108). A review by Goldin et al. (60) of response in terms of schedule of administration, using data compiled by Livingston and Carter (89), shows no evident schedule dependency (Table 8). The apparent inferiority of weekly IV use is probably not meaningful because of the small number of patients involved. The measurement of response by survival alone seems attractive since it is a clearcut and easily defined endpoint but variability is still a significant problem. Selawry and Hansen (109) have shown that the median survival of successive cohorts of 60 0r more patients treated with placebo by the same physicians varies by more than 50%, even when eases are staged and divided into those with regional and limited disease. The survival endpoint has been used in many studies of CTX made by the VA Lung Cancer Study Group. When some of these controlled trials (Table 9) are examined~ CTX yields an apparent survival gain over placebo in small cell carcinoma (108). However, the data are quite variable in the remaining three trials of CTX vs. asparaginase, probably due to the relativelysmall number of patients. This variability is disturbing and makes it difficult to reach a conclusion on the value of CTX. Combination chemotherapy. CTX has been widely evaluated in combination drug regimens for the treatment of lung cancer. Several of these are reported to have increased objective regression rates but their impact on survival has been minimal and none are standard therapies. Selected data on some of the recent combinations are outlined in Table 10. The Eastern Cooperative Oncology Group (51) has demonstrated a statistically significant increase in Objective response using CTX + CCNU in small cell carcinoma. The resPonse is greater than the additive effects of the two agents and does not extend to identically treated patients with adenocarcinoma.

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S. K. CARTER AND R. B. LIVINGSTON Table 7. Objective r e s p o n s e rate w i t h c y c l o p h o s p h a m l d e in various cell t y p e s o f lung cancer (108)

Cell type

No. patients treated Response rate (%)

Epidermoid Small cell Adenocarcinoma Large cell

232 296 48 22

20 31 21 23

T a b l e 8. Objective r e s p o n s e rate w i t h c y c l o p h o s p h a m l d e in l u n g cancer a c c o r d i n g to s c h e d u l e o f a d m i n i s t r a t i o n (60)

Schedule IV loading course + PO maintenance Chronic daily PO or IV to toxicity Weekly IV High single dose intermittent

No. patients treated Response rate (%) 317 93 40 35

34 39 10 40

T h e studies of Selawry and his co-workers (71, 110) show significant superiority of a 3-drug regimen of C C N U + C T X + M T X over the latter two drugs alone. This superiority was evidenced by an increase in the time to progressive disease (time to change of treatment regimen) from 3 to 6 months, accompanied by increased median survival from 5.7 to 8.3 months for small cell carcinoma and significant extension from 4.5 to 8 months for those with adenocarcinoma. I n each case, there was also an impressive increase in response rate and markedly prolonged survival in responders as compared to non-responders. Results could be further improved by more frequent administration of C C N U (23, 76). T h e Swiss Chemotherapy Group (3, 4) evaluated a controlled trial of 4 drugs (procarbazine, C T X , M T X and V C R ) used simultaneously or in sequential 2-week courses. Simultaneous administration was significantly superior to the sequential regimen in obtaining objective response in small cell carcinoma; there was a suggestion of superiority for the simultaneous drugs in the epidermoid cell type. Livingston et al. (90) have reported on a 4-drug combination ( " C O M B " ) consisting of C T X , V C R , M e C C N U and bleomycin. Responses were obtained in 11 of 33 patients with squamous lung cancer and in 13 of 15 with small cell lesions. T h e median survival was 30 weeks in small cell carcinoma but was no better than historical placebo controls in the squamous cell type. Combined modalities. Radiotherapy and C T X have been combined in m a n y studies, most of which showed either no advantage or statistically insignificant advantage or disadvantage for the combination (61, 62, 65, 74, 107, 122). Only two investigators report positive results (Table 11). T h e study of Bergsagel et al. (13) indicates a modest 42 % gain in median survival for patients on radiotherapy + C T X over those receiving radiotherapy alone. T h e survival gain for the subgroup of patients with small cell carcinoma exceeded 100% (from 5 to 10+ months), as might be expected because of the known sensitivity of this tumor to either component of the therapy. Spacing of the drug doses at 3-week intervals was less immunosuppressive than daily or weekly medication. Use of eight C T X doses was not better than limitation to four

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Table 11. Controlled trials o f C T X + r a d i o t h e r a p y w i t h p o s i t i v e r e s u l t s in l u n g c a n c e r

Investigator Bergsagelet al. (13)

Brouet el al. (24)

Treatment

No. pts

Survival

RT: 4000-5000R]4-5 wk

42

MST 7.2 mos

RT + CTX (1 g/m2 q 3 wk x 4) R T + CTX (1 g/m2 q 3 wk x 8)

38 } 35

MST 10.2 mos

RT: 6000 R/6 wk RT + CTX (200 mg/d • 5/wk)

48 46

31% (1 yr) 35%

doses, which attests to the importance of optimum duration of chemotherapy in addition to optimum dose and schedule. In the second study (24), conducted by the European Organization for Research and Treatment of Cancer ( E O R T C ) , the superiority of adjuvant chemotherapy would have been overlooked if only routine chest films had been used to detect tumor regression. Endobronchial observation alone showed a higher response rate for combined therapy. The combination of chest films and endobronchial observation produced discordant findings in several patients, i.e. endobronchial regression without regression on chest films or vice versa. Elimination of the discordant patients from evaluation revealed a statistically significant difference in tumor regression of 29O/o for radiotherapy alone versus 78% for combined treatment. Unfortunately, this difference was not reflected in the l-year survival. Two other studies suggest superiority of adjuvant chemotherapy over radiotherapy alone but they fall short of statistical significance (74, 122). The positive findings for adjuvant C T X are in contradistinction to those of a very similar study (107) that employed 5 to 7 spaced doses of C T X (700-1600 mg/m 2) given to a total dose of 10 to 14 g. For unknown reasons, neither the median nor long-term survival favored CTX. Another study (65), with a different dose schedule of C T X , also showed no benefit by the adjuvant treatment. Three studies have evaluated C T X as a surgical adjuvant in bronchogenic carcinoma (Table 12). Prognostic values employed in previous studies are applicable in that most patients were separated into the category of curative or palliative resection. The VA Surgical Adjuvant Group (73) used the same definitions employed in a prior study of nitrogen mustard. The number of patients studied by the VA group seems inordinately overweighted toward a curative resection as if some process of selection was occurring. Poulsen's curative resection category (98) should actually be termed curative with poor prognosis since it included cases in which local invasion was observed in the pericardium or diaphragm when the excision was apparently radical, i.e. for cure. Brunner et al. (26) used criteria that were truly curative since cases were excluded post-operatively if there was doubt as to the curability of the resection. Neither the VA group (73) nor Poulsen (98) considered the influence of cell type on results. There was no stratification for cell type in the VA study, while Poulsen had significant data for only squamous cell carcinoma. Brunner et al. (26) did stratify their patients by cell type but the numbers in each group were small, especially for small cell carcinoma. The usual criticism in terms of treating to toxicity can be made in the studies made by the VA and by Poulsen, but not in that of Brunner et al. (26) which may h.ave been the

312

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only group to use the drug to its full toxic potential. Eighty per cent of their patients developed leucopenia, while in the other studies the incidence was only about 30%. This may have been significant in terms of results, since in the study ofBrunner et al. (26) unfavorable results were attributed to immunosuppression. Both the VA group and Poulsen administered at least a portion of the dose in the first course by "directed" systematic application, i.e. intrapleurally or intra-arterially. In view of the effect of alkylating agents on cell kinetics, none of the studies used intermittent spaced doses that theoretically, according to animal models, would affect the most effective use of the drug. T h e survival data (Table 12) for the study of the Swiss group (26) had to be extrapolated from the text of their paper since most of the tabular data measured percentage recurrence. This was felt to be a more valuable criterion for the effectiveness of adjuvant chemotherapy than lifespan, which may be influenced by additional therapy after recurrence. Thus, at least in the Swiss study, it is apparent that other therapy used at time of recurrence makes it difficult to obtain true comparisons of data. It is evident that the 3-year survival in the Swiss group study is approximately double that of the next best results obtained by Higgins et al. (73). This must be attributed to selection since the patients in the Swiss study were randomized after surgery, while those in the VA study were randomized at surgery. In terms of results, the chemotherapy patients in the Swiss study did worse than controls. Although it was reported to be a statistically significant difference, the numbers are not very convincing and this failing is further supported by the lack of difference in median survival between the C T X treated and untreated patients. I f C T X was really so detrimental, one would wonder why that group did not show a significant difference in survival. This might be explained by the other chemotherapy used at recurrence, which must have reversed the trend, but unfortunately the nature of this therapy is not known. Percentage recurrence could not be correlated with cell type. Also, there was no direct correlation with the degree of leucopenia and recurrence rate. Thus, assuming C T X was definitely detrimental, one might wonder if some mechanism other than immunosuppression might have been operative and not reflected in the degree of leucopenia (i.e. leucocyte mobilization ? leucocyte migration ?). In summary, C T X produced no benefit over placebo in randomized controlled trials. In terms of survival, there was no significant difference between treatment and control except in the Swiss study which appeared to demonstrate lower survival in the C T X treated groups. However, flaws in study designs, including suboptimal use of drugs, differences in defining curative procedure and differences in evaluation make it difficult to compare the three studies. Gynecologic tumors Ovary. Alkylating agents have been extensively evaluated in patients with advanced ovarian cancer and now are the most active class of drugs commonly used against this tumor. Presently available data do not suggest that any particular agent is superior to another. C T X has been among the most vigorous of the alkylating agents evaluated although melphalan would have to take first place. The overall response rate for C T X is 43% in 284 eases (Table 13). The study of Beck and Boyes (12) is the most extensive, showing 49 % overall response among 126 patients, and includes a 75 % response rate in previously untreated patients but only 42 % response in those refractory to radiotherapy or relapsing after its use.

CYCLOPHOSPHAMIDE IN SOLID TUMORS

315

T a b l e 13. C T X i n o v a r i a n c a n c e r

Investigator Beckand Boyes (12) Shnider et al. (I I 1) Coggem el al. (36) Rundles et al. (105) Atkins et al. (9) Anderson (6) Decker et al. (45)i Livingston and Carter (89) Hreshchyschyn (75) Young et al. (125)

Dose 200 mg/d x 10 IV or 50-100 mg/d PO Varied 7.5 mglkg/d x 6 IV. Then, 6-20 mglkg/wk or twice weekly or 45-100 mg/kg x 1 IV 10-20 mg/kg/d IV to total 40 mg]kg. Then, 100-250 mg/d PO 30-40 mg/kg over 5-10 days IV. Then, PO daily as tolerated. 100 mg/d PO 400 mg/d • 4 IV. Then, 50-150 mg/d PO maintenance Variedw 2-20 mg]kg/d IV or 15 mg]kg/wk IV 40 mg/kg q 12 h • 2 every 3-4 wk

Total

No. of evaluable . patients 126 22 9

Response ^ No. % 62 7 6

49 32 66

13

1"~

8

7

6+*

86

17 40

12 3

70 7

28 12 10

18 2 6

64 16 60

284

123

43

1"Complete remission. ++4 responses > 2 mos duration. w8 separate small studies. Y o u n g et al. (125) c o m p a r e d a high I V dose C T X regimen to standard use o f oral melphalan. T h e response rates were not different, nor were the m e d i a n durations o f initial remission or survival. T h e M a y o Clinic group (78) performed a controlled r a n d o m i z e d trial in Stage I I I and I V disease c o m p a r i n g response and survival rates obtained with C T X alone or combined with radiotherapy versus whole a b d o m i n a l irradiation alone. T h e r e was no statistical difference in survival time a m o n g the three treatment groups. Decker (44), at the M a y o Clinic, also studied C T X as an a d j u v a n t to a b d o m i n a l r a d i o t h e r a p y in a d v a n c e d ovarian cancer. Thirty-five patients were r a n d o m i z e d to receive a total of 3500 rads over 4 weeks versus the same radiotherapy plus oral C T X . T h e r e was a m e d i a n survival of 13 months in the C T X g r o u p a n d 7 months for X - r a y alone. Cervix. T h e c h e m o t h e r a p y of a d v a n c e d squamous cell c a r c i n o m a of the cervix usually follows extensive p r i m a r y treatment by high dose pelvic irradiation, radical surgery or both, T h e lack of a truly effective d r u g or d r u g combination for treating the local recurrence that usually takes place in previously heavily treated tissue has m a d e the t h e r a p y o f this disease extremely disappointing. C T X is the most extensively studied agent (Table 14), with an overall response rate o f 19% in 187 cases. Solidoro et al. (I 14) obtained a 21 ~o response rate in 42 patients using a dose of 3-4.5 mg/kg/d I V administered until the white cell count was 50 % decrease in measurable disease, the rate falls to 5 % (1 ] 19). However, it should be emphasized that these later studies used the drug on the high dose intermittent schedule. Table 15. CTX in m e l a n o m a

Criteria of response

Responserate

Reference

Vague >50% decrease

22% (8136) 5% (l/19)

14, 36, 55, 69, 85, 105, 115 27, 64, 86

Total

16% (9/55)

C T X has been included in some combination chemotherapy approaches (Table 16) but none of these have been evaluated to an extent warranting use as established therapy. H e a d and neck tumors

There apparently is some evidence in the literature supporting the concept that C T X is active in squamous cell tumors of the head and neck region (Table 17). The largest Series (72) employed a variety of routes of administration, including IV, PO and IA, and obtained a 39% response rate (including 2 CR) among 56 cases. Unfortunately, response is not reported in terms of the dose schedule used. The other 4 series are small (total 21 cases) and overall response is 36% (28/77). Combination chemotherapy has not been aggressively pursued in this disease.

CYCLOPHOSPHAMIDE IN SOLID T U M O R S

317

T a b l e 16. G~rx i n c o m b i n a t i o n d r n g r e g h n e n s for mml;~qmant m e l a n o m a

Investigator

Response ^ % No. (CR + PR)

No. of evaluablc patients

Regimen

9

0

0

C T X (750 mg/m2/d x I) DTIC (850 mg/m2/d x 1) VCR (2 mg/m 2 q 4 wk)

20

5

25

Costanzi and Coltman (41)

CTX (300 mg d 1 and d 5) VCR (0.025 mg/kg d 2 and 5) M T X (0.5 mg d 1 and 4) 5-FU (10 mg/kg/d x 5)

10

6

60

Coltman et aL (37)

GTX (2{)0-300 mg d 1 and 5) VGR (0.015 mg/kg d 2 and 5) M T X (0.25 mg/kg d 1) 5-FU (7.5 mg/kg/d x 5)

7

2

28

Hanharn r al. (70)

CTX VCR MTX 5-FU

10

0

0

Ramirez (99)

C T X (2 mg/kg/d) V C R (0.02mg/kg/wk) M T X (0.5mg/kg/wk) 5-FU (I0 mg/kg/wk) Prednisone (45 mg/d x 2 wk; then, 30 mg/d • 2 wk; then, 15 rag/d)

23

5

22

Johnson and Jacobs (79)

C T X (2 mg/kg/d x 28) V C R (25/tglkg/wk)

Gardere et aL (58)

T a b l e 17. ~

(200-300 mg d 1 and 5) (0.015mg/kg d 2 and 5) (0.25mg/kg d I) (7.5 mg/kg/d x 5)

in h e a d a n d n e c k t u m o r s

Investigator

Dose

No. of cvaluable patients

Harrison et at. (72)

40 mg/kg IA, single dose, or 4 mg/kg/d PO to limiting toxicity, or 4 0 - 6 0 mglkg/d IV to limiting toxicity

Bergsagel and Lcvin (14)

0.8-9.3 mg/kg/d • 5-35 IV; then PO maintenance

56

S h n i d e r et al. (111)

Varied

10

Varied

4

Solomon et al. (115)

100-200 mg/d PO or 30 mg/kg • 1 IV followed by 10-15 mg/kg at 1-2 wk intervals after WBC recovery to ~4000

3

Including 2 CR.

A

No.

%

22t

39

4

Foye et aL (56)

Total

Response r

m

_ _

_ _

77

28

36

318

S.K. CARTER AND R. B. LIVINGSTON

Urologic cancer

A recent review by Carter and Wasserman (33) shows that evaluation of chemotherapeutic agents in the urologic malignancies has not been very widespread. In prostatic cancer the testing of non-hormonal compounds has been minimal and not one of the 30 standard antitumor drugs reviewed by Carter and Wasserman had been evaluated in more than 66 cases. Most of the available data are from Phase I studies or from trials in patients with far-advanced disease. Despite this, C T X , as well as nitrogen mustard and 5-FU, exhibits hints of activity that make one cautiously optimistic that prostatic adenocarcinoma will not be a tumor totally unresponsive to drug treatment. T h e overall response rate for C T X is 14% (8/57) in a variety of studies, none of which included large patient numbers. Unfortunately, chemotherapy also has not been intensively studied in bladder carcinoma (33). Most of the data have been gathered in large studies devoted to the effectiveness of specific drugs in a broad range Of tumors, which generally include only a few cases of bladder cancer. While these drug-oriented studies provide some idea of the potential efficacy o f a n d t u m o r drugs in bladder cancer, they establish practically nothing concerning the prognostic criteria that might favor the use of chemotherapy in this disease. T h e alkylating agents have been only minimally tested in bladder cancer by systemic routes of administration (Table 18). C T X and ehlorambucil have both been administered to 10 patients but the data are insufficient for a n y definitive conclusion.

Table 18. Activity of alkylating agents in bladder cancer

Investigator Cyclophosphamide Shnider et al. (111) Fox (54)

Dose schedule

Varying (a) 400-500 mg/d IV to WBC of 1000/ram3; then PO maintenance as tolerated after marrow recovery (b) 200-800 mg/d IV x 6; then PO maintenance as tolerated after marrow

No. of evaluable patients

Response ^ rNo. %

2

0

8

2'f

2 8

0 0

25

recovery

Chlorambucil Gumport et aL (68) Moore et al. (93)

Varying daily dose 0.2 mg/kg/d x 42 as tolerated

M

~"Response durations < 1 month.

Gastrointestional cancer

C T X has received some evaluation in adenocarcinoma of the large bowel (Table 19) (31). T h e overall response rate (27 %) includes some G e r m a n data for which the response criteria are unclear and the question of concommitant therapy with the C T X can be raised. I f this data is not considered, the response rate ( 1 5 / 7 1 - 2 1 % ) is comparable to what is reported for other "active" drugs.

CYCLOYI-IOSPHAMIDE IN SOLID TUMORS

319

Table 19. C T X l n large b o w e l cancer (31)

Dose schedule

No. of evaluable . patients

Response ^ No. %

IV daily x 5-6; then, PO maintenance High dose intermittentt High dose intermittent~. IV weekly

32 18 32 7

6 9 9 0

19 50 28 0

Total

89

24

27

German data. +*U.S. data. Conclusion

C T X has a wide r a n g e of activity against solid tumors ( T a b l e 20). I t is clearly active i n 5 m a j o r tumors (breast, lung, ovary, cervix a n d sarcomas) a n d there is evidence of activity i n 3 others (colon, head a n d n e c k a n d prostate), a l t h o u g h it is n o t clearly established. O n l y in m a l i g n a n t m e l a n o m a c a n it be said t h a t C T X is inactive a n d even here the p a t i e n t n u m b e r s are n o t large. I n the r e m a i n i n g solid tumors the d a t a are i n a d e q u a t e for a n y conclusion o n the efficacy of C T X . Table 20. CTX activity in s o l i d t u m o r s

No. response CTX activityt

++

+ --

NE

Tumors

No. evaluable pts

Response rate (%)

Lung Breast Ovary Cervix Sarcoma Colon Head & Neck Prostate Melanoma Pancreas Stomach Bladder Kidney Esophagus Brain Testicle Uterus

303/1513 182/529 1151262 36/187 48/93 15/71 28/77 8/57 9/55 1/5 0/4 2/10 2/12 -0/!4 2/2 4/16

20 34 44 19 52 21 36 14 16 -------25

t Definite acdvity (++) : evidence of activity but not clearly established (+) ; inactive (--) ; not evaluated (NE). References

1. Acute Leukemia Group B. (1960) CanterChemother.Rep. 8:116. 2. Ahmann, D. (1975) Personal communication. 3. Alberto, P. (1973) CanterChemother.Rep. (part 3) 4 (no. 2): 199.

320

S.K. CARTER AND R. B. LIVINGSTON

4. Alberto, P., Brunner, K., Martz, G., et al. (1970). Proc. lOth Int. Cancer Congr., Houston, Texas, p. 469. 5. Anders, C.J. & Kemp, N. H. (1961) Br. reed.3". 2: 1516. 6. Anderson, T. (1965) In Fairly, G. & Simister, J. (Eds) Cyclophasphamidepp. 92-97. Baltimore: Williams & Wilkins. 7. Arnold, H. & Bourseaux, F. (1958) Angew. Chem. 70: 539. 8. Arnold, H., Bourseaux, F. & Brock, N. (1958). Naturwissenschaften 45: 64. 9. Atkins, H. L., Gregg, I-L L. & Hymann, G. A. (1962)Cancer 15: 1076. 10. Aubrey, D. A. (1970) Br. med. J. 3: 588. I1. Barren, K., Helm, W. & King, D. (1965) Br. reed.J. 2: 686. 12. Beck, R. & Boyes, D. (1968) Can. med. Ass. J. 98: 539. 13. Bergsagel, D. E., Jenkins, R. D. T., *Pringle,J. F., White, D. M., Fetterly, J. C. M., Klasscn, D. & McDermot, R. S. R. (1972) Cancer 30: 621. 14. Bergsagel, D. E. & Levin, W. C. (1960) CancerChemother. Rep. 8: 120. 15. Bergsagel, D. E., Robertson, G. L. & Hasselback, R. (1968) Can. med. Ass. J. 98: 532, 16. Blum, R. It. & Carter, S. K. (1974) Ann. intern. Med. 80: 249. 17. Blumenschein, G., Cardenas, J., Freireich, E. & Gottlieb, J. (1974) Proe. Am. Soc, din. Oncol, 15: 193. 18. Brennan, M. & Talley, R. (1967) In Current Concepts in Breast Cancer p. 225. Baltimore: Williams & Wilkins Co. 19. Brock, N. (1958) Arzneimittel-Forsch. 8: 1. 20. Brock, N. & Hohorst, tt.J. (1962) Naturwissenschaften 49: 610. 2i. Brock, N. & I-Iohorst, H. J. (1963) Arzneimittel-Forsch, 13: 1021. 22. Brock, N. & Wilmanns, H. (1958) Dt. med. Wschr. 83: 453. 23. Broder, L. & Hansen, H. H. (1973). Eur. J. Cancer 9: 147, 24. Brouet, G., Flament, R. & t-Iayat, M. (1968). Eur. J. Cancer 4: 129. 25. Brouet, G., Flament, R. & t-Iayat, M. (1968) Eur. J. Cancer 4: 437. 26. Brunner, K. W., Marthaler, T. & Muller, W. (1971). Eur. J. Cancer 7: 285. 27. Buckner, C. D., Rudolph, R. H., Fefer, A., Clift, R. A., Epstein, R. B., Funk, D. D., Neiman, P.E., Sliehter, S.J.,Storb, R. & Thomas, E. D. (1972) Cancer 29: 357. 28. Bull, J., Tormey, D., Falkson, G., Blom, J., Chang, K. S. S. & Carbone, P. P. (1974) Pror Am. Ass. CancerRes. 15: 118. 29. Carbone, P. (1975) Personal communication. 30. Carter, S. K. (1972)Cancer30: 1543. 31. Carter, S. K. & Friedman, M. A. (1974) Cancer Treat. Rev. 1: 111. 32. Carter, S. K. & Soper, W. T. (1974) Cancer Treat. Rev. 1: 1. 33. Carter, S. K. & Wasserman, T. (1975) Cancer, 36: 729. 34. Chabner, B. A., Myers, C. E., Coleman, C. N. & Johns, D. G. (1975) New Engl. J. Med. (in press). 35. Coates, A. (1970) Aust.-N.Z.J. Obstet. G!mec. 10: 33. 36. Coggins, P. R., Ravdin, R. G. & Eisman, S, H. (1960) Cancer 13: 1254. 37. Coltman, C. A., Costanzi, J. J., Dudley, G. M., I-Iaut, A., Lane, M. & Gehan, E. A. (1971) Am. J. med. Sci. 261; 73. 38. Colvin, M., Padgett, C. A. & Fenselau, C. (1973) CancerRes. 33: 915. 39. Connors, T. A., Cox, P.J., Farmer, P. B., Foster, A. B. & Jarman, M, (1974) Biochem. Pharmac. 23: 115. 40. Cooper, R. (1969) Proc. Am. Ass. CancerRes. 10: 15. 41. Costanzi, J.J. & Coltman, C. A., Jr (1967) Cancer 23: 589. 42. Davis, H. L., Ramirez, G., Ellerby, R. A. & Ansfield, F.J. (1973) Cancer 34: 239. 43. Davis, It. L., Ramirez, G., Korbitz, B. C. & Ansfield, F.J. (1970) Dis. Chest 56: 494. 44. Decker, D. G., Mussey, E., Malkasian, G. D. & Johnson, C. E. (1967) Am. J. Obstet. G!tnec. 97: 171. 45. Decker, D. G., Malkasian, G. D., Mussey, E. & Johnson, C. E. (1967) Am. J. Obstet. Gyncc. 97: 656. 46. DeFronzo, R. A., Braine, I-I., Calvin, O. M. & Davis, P.J. (1973) Ann. intern. Med. 78: 861. 47. DeLena, M., DePalo, G. M., Bonadonna, G., Beretta, G. & Bajetta, E. (1973) Tumori 59:11. 48. DeWys, W. (1968) Proc. Am. Ass. CancerRes. 9: 18. 49. Dietrich, R. A. (1966) Bioehera. Pharmac. 15: 1911. 50. Dorsk, B. M., Kaufman, R.J., Winn, R.J., Robbins, G. F. & Ochoa, M., Jr., (1972) Pror Am. Ass. Cancer Res. 13: 30. 51. Edmonson, J. H. & Lagakos, S. W. (1974) Proc. Am. Ass. Cancer Res. 15: 180.

CYCLOPHOSPHAMIDE IN SOLID TUMORS 52. 53. 54. 55. 56. 57. 58. 59.

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Fairley, K. F., Barrie, J. V. &Johnson, W. (1972) Lancet 1: 568. Foley, J. F. & Kennedy, B.J. (1964) CancerChemother. Pep. 34: 55. Fox, M. (1965) Br. J. Urol. 37: 399. Foye, L. U., Chapman, C. C., Willett, F. M. & Adams, W. S. (1960) Cancer Cheraother. Re/,. 6: 39. Foye, L. U., ChaPman, C. C., Willett, F. M. & Adams, W. S. (1960) Archs. intern. Med. 106: 365. Friedman, D. M. & Seligman, A. M. (1954) J. Am. Chem. Soc. 76- 655. Gardere, S., Hussian, S. & Cowan, D. H. (1972) CancerChemother. Pep. 56; 357. Gold, G. L., Shnider, B. I., Salvin, L. G., Sehneiderman, M. A., Colsky, J., Owens, A. H., Krant, M.J., Miller, S. P., Frei, E., Hall, T. C., Spurr, C. L., Mclntyre, O. R. Hoogstraten, B. & Holland, J. F. (1970) J. Clin. Pharmac. 10: 110. 60. Goldin, A., Carter, S. K. & Mantel, N. (1974) In Sartorelli, A. C. & Johns, D. G. (Eds) Handbook of Experimental Pharmacology, p. 12. Berlin-Heidelberg-New York: Springer-Verlag. 61. Go!lin, F. F., Ansfield, F. J., Curreri, A. R., Heidelberger, C. & Vermund, H. (1962) Cancer 1St 1209. 62. Gollin, F. F., Ansfield, F.J. & Vermund, H. (1967) CancerCheraOther. Pep. 51: 189. 63. Gordon, I. & McArthur, J. (1965) Scott. Med. J. I0: 27. 64. Gottlieb, J. A., Mendelson, D. & Serpick, A. (1970) CancerChemother. Pep. 54: 365. 65. Green, R. A., Humphrey, E., Close, H., & Patno, M. E. (1969) Am. J. reed. 46: 516. 66. Greenspan, E. (1966) J. Mt Sinai Hosp. 33: 1. 67. Greenspan, E. (1963) J. Mt Sinai Hosp. 30: 246. 68. Gumport, S., Golomb, F. & Wright, J. (1958) Ann. N.Y. Acnd. Sd. 68: 1024. 69. Haar, H., Marshall, C.J., Bierman, H. R., & Stenfeld, J. L. (1960) CancerChtmother. Pep. 6: 41. 70. Hanham, L W. F., Newton, K. A. & Westbury, G. (1971) Br. J. Cancer 25: 462. 71. Hansen, H. H. & Selawry, O. S. (1974) Proc. X I Int. CancerCongr., Florence, Italy. 72. Harrison, D., Espiner, H. & Glazebrook, G. (1965) In Fairley, G. & Simister, J. (Eds) Cydophasphamide, pp. 48-55. Baltimore: Williams & Wilkins. 73. Higgins, G. A., Humphrey, E. W., Hughes, F. A. & Keehn, R.J. (1969) J. Surg. Oncol. 1: 221. 74. Hoest, H. (1973) CancerChemother. Pep. (part 3) 4 (no. 2) : 161. 75. Hreshchyschyn, M. M. (!973) Gyncc. Oncol. It 220. 76. Israel, L. & Chahinian, P. (1973) Eur. d. Cancer 9: 799. 77. Jacobs, E. M., Peters, F. C., Luce, J. K. etal. (1968) J. Am. ra,d. Ass. 203: 392. 78. Johnson, C. E., Decker, D. G., Van Herik, M., Mussey, E., Malkasian, G. D. & Jorgensen, E. O. (1972) Am. J. Roentg. Rad Ther. nud. M~d. 114: 136. 79. Johnson, F. D. & Jacobs, E. M. (1971) Cancer27: 1306. 80. Johnson, W. W. & Meadows, D. C. (1971) New Engl. J. Med. 284: 290. 81. Kaung, D. T., Wolf, J., Hyde, L. & Zelen, M. (1974) CancerChtmother. Pep. 58: 359. 82. Kennedy, B.J. (1969) Cancer24: 1345. 83. Kmetz, D. R. & Newton, W. A. (1964) Pror Am. Ass. CancerPes. 5: 36. 84. Kontras, S. B. & Newton, W. A. (1961) CancerChemother. Rep. 12: 39. 85. Korst, D. R., Johnson, D. F., Frenkel, S. P. & Challeneh, W. L. (1960) CancerCh_onother. Pep. 7: 1. 86. Larson, R. R. & Hill, C.J. (1971) Am. d. Surg. 122: 36. 87. Lemkin, S. R. & Dollinger, M. R. (1973) Proc. Am. Ass. Cancer Pes. 14: 37. 88. Leone, L. A. & Rege, V. A. (1973) Proc. Am. Ass. CancerPes. 14: 125. 89. Livingston, R. B. & Carter, S. K. (1970) Single Agents in Cancer Chemotherapy. New York, Washington and London : IFI/Plenum. 90. Livingston, R. B., Einhorn, L. H., Bodey, G. P. et al. (1975) Cancer (in press). 91. Lokich, J.J. & Skarin, A. T. (1972) CamerChemother. Pep. 56: 761. 92. McLean, R. (1965) Thorax 20: 555. 93. Moore, G., Bross, L D. J., Amman, R. Nadler, S., Jones, R., Slack, H. & Rimm, A. A. (1968) Cancer Chemother. Pep. 52: 661. 94. Nemoto, R. & Dao, T. (1971) New York J. Med. 7It 554. 95. Nissen-Meyer, R., Kjellgren, K. & Masson, B. (1971) CancerChemother. Pep. 55. 561. 96. Pegg, D. E. (1963) CancerChemother. Pep. 27: 39. 97. Philips, F. S., Sternberg, S. S., Cronin, A. P. & Vidal, P. M. (1961) CancerRes. 21: 1577. 98. Poulsen, O. (1962) J. Int. Coll. Surg. 37: 177. 99. Ramirez, G. Personal communication. 100. Ramirez, G. (1973) CancerChemother. Pep. 57: 95.

322

S.K. CARTER AND R. B; L I V I N G S T O N

101. Ramirez, G. (1973) Proc. Am. Ass. CancerRes. 14: 17. 102. Ravdin, R. & Eisman, S. (1967) In Current Concepts in Breast Cancer, p. 200. Baltimore: Williams & Wilkins Co. 103. Reeve, T.S.(1961)~Med. ft.Aust. 1: 686. 104. Rubin, J. S. & Rubin~ R. T. (1966) J. Urol. 96: 313. I05. Rundlcs, W. R., Laszlo,J, Garrison, F. E. & Hobson, J. B: (1962) Cancer Chemother. Peep. 16" 407. 106. Salmon, S. &Jones, S. (1974) Proc. Am. Ass, CancerRes. 15: 90. 107. Scheurlcn, H , Drings;~P.,Vollhabcr,M . M., Kuttig, C. & Wicland, C. (1972) Strahlentherapie143: 154. 108. Sclawry, O. S. (1975) In Isracl,L. (Ed.) Lung Cancer Facts, Concepts and Strategies.N e w York-Basel: S. Kargcr (in prcss). 109. Sclawry, O. S,& ~'lanscn,H. H. (1973) In Holland, J. & Frci,E. (Eds) CancerTVIedieine,p. 1473.Philadelphia: Lea & Fcbigcr. II0. Sclawry, O. S., Hanscn, H. H., Carr, D. T., Scaly,R. & Simon, R. (1974) Proc. Am. Ass. Cancer Res. 15:118. 111. Shnider, B., Gold, G., Hall, T. and Eastern Cooperative Group (1960) CancerC~mother. Rep. 8: 106. 112. Smalley, R. V., Murphy, S., Chart, Y. K., Hugulcy, C. M.,Jr (1973) CancerChemother. Rep. 57: 110. 113. Smlth, J. P., Ruttedge, F., Burns, B; C. & Soffar, S. (1967) Am. d. Obstet. Gynec. 97: 800. 114. Solidoro, A. S., Estcves, L., Castcllano, C., Valdivia, E. & Barriga, O. (1966) Am. d. Obstet. Gyncc. 94: 208. 115. Solomon, J., Alexander, M.:J. & Stelnfeld, J. (1963) J. Am. med. Ass. 183: 165. 116. Spear, P. & Patno, M;: (1962) GancerChemother. Rep. 16: 413. 117. Stoll, B. A. & Matar, J . H . ( 1961) Br. med. or. 2: 283. I t8. Stott, P. B., Zelkowitz, L. & Tucker, W. G. (1973) CancerChemother. Rep. 57: 106. 119. Sweency, M. J , Tuttle, A. H., Etteldorf, J. N. ; Whittington, G. L. (1962) J. Pediat. 61: 702. 120. Thurman, W. G., Fcrnbach, D.J. & Sullivan, M. P. (1964) New Engl. J. Med. 270" 1336. 121. Trcves, N. & Finkbeincr, J. A. (1958) Cancer 11: 421. 122. Tucker, R. D., Scaly, R., vanWyk, C., LeRoux, P. L. M. & Soskotne, C. L. (1973) Cancer Chemother. Rep. (part 3) 4 (no. 2) : 159. 123. Vaughn, C. B., Baker, L. H., A1-Sarraf, M., Vaitkevicius, V. K. (1973) Cancer Chemother. Rep. 57: I11. 124. Wall, R. L. & Conrad,.F, G. (1961) Archs. intern. Med. 108: 456. 125. Young, R. G., Canellos, G. P., Chabner, B. A., Sehein, P. S., Hubbard, S. P. & DeVita, V. T. (1974) Gynec. Oncol. 2: 489.