Int. J. Cancer: 51,.58-61 (1992) 0 1992 Wiley-Liss, Inc.
Publication of the International Union Against Cancer Publicationde I'Union lnternationale Contre le Cancer
CA125-RESPONSE ASSESSMENT IN EPITHELIAL OVARIAN CANCER D.J. CRUICKSHANK', P.B. TERRYand W.T. FULLERTON Department of Obstetrics and Gynaecology, University of Aberdeen, Royal Infirmary, Aberdeen AB9 2ZB, Scotland. To assess the clinical potentialof serial serum CAI 25 measurements in the follow-up of patients with epithelial ovarian cancer, 74 consecutive unselected patients with histologically confirmed ovarian carcinomawere studied prospectively. There was an 83Oh concordance between clinical assessment and CAI 25 assessmentof response. The positive predictivevalues of a rising CA I25 for disease progression and a falling CA I25 for disease regression were 0.93 and 0.94, respectively. The absolute CAI 25 values during observations of complete response (mean 96 U/ml; 95% confidence interval; 33 to 128 U/ml), partial response (mean 134 U/ml; 95% confidence interval; 98 to I59 U/ml) and stable or progressive disease (mean 39 I U/ml; 95% confidence interval; 282 to 545 U/ml) were significantly different. A randomized study is required to determine whether CAI25 monitoring has any benefit in terms of outcome, and particularlysurvival, in epithelial ovarian cancer.
Epithelial ovarian cancer is an insidious disease which spreads locally in the pelvis and diffusely over the peritoneal surfaces of the abdominal contents. As a result, monitoring of disease status in response to chemotherapy after surgery, using standard imaging techniques (ultrasound, computerized axial tomography and magnetic resonance imaging), is unreliable. It has been suggested that computerized axial tomography is the most informative non-invasive method for monitoring response (Johnson et al., 1983). However, the sensitivity of this test depends not only on the size of the residual or recurrent disease but also on its site. In addition, it is an expensive and impractical means of monthly response evaluation. The pressure for surgical response data in phase-3 studies highlights the deficiencies in the clinical assessment of response (Cohen et al., 1983). If the combination of cis-platinum and cyclophosphamide produccs a 74% response rate, then 26% of patients with advanced disease will be resistant to treatment (Neijt et al., 1987). Nevertheless, it is unusual for patients to be withdrawn from phase-3 studies because of progressive disease on treatment, the reason being the extent of non-evaluable or nonmeasurable residual disease (up to 80%) after cytoreductive surgery which is unsuitable for monitoring by standard imaging modalities. Resistant small-volume rcsidual disease progresses unnoticed during treatment. The 17th Study Group of the Royal College of Obstetricians and Gynaecologists stated that a major priority was the development of reliable methods of monitoring patients being treated for ovarian cancer. The antigenic determinant CA125 has been extensively studied in epithelial ovarian cancer. Pre-operative serum levels correlate with tumour load and all epithelial sub-types are associated with elevated levels (Cruickshank et al., 1987). The sensitivity of CA125 in ovarian cancer is over 80% in most published series (Cruickshank et al., 1987; Bast et al., 1983; Canney et al., 1984; Kivinen et al., 1986; Li-juan et al., 3986; Krebs et al., 1986; Alvarez et al., 1987; Vergote et al., 1987; Lavin et aL, 1987; Sevelda et al., 1987; Brioschi et al., 1987; Altaras et al., 1988). There is great difficulty, however, in interpreting and comparing the majority of these studies. They are largely retrospective, using stored serum banks. Most populations studied are patients with advanced disease and are dependent on oncology referral patterns, with a bias for bulky residual disease or recurrent disease. Such biases would tend to present CA12.5 in a favourable light. Some studics exclude mucinous carcinomas, while others include tumours of low malignant potential or indeed non-epithelial ovarian
cancers. There is also the problem of quality control, with different commercially available CA125 kits and assay methods being used by different workers. With particular reference to monitoring, most studies fail to define significant CA125 changes or response criteria, and many do not use internationally accepted criteria for clinical response assessment (World Health Organization, 1979). The aim of this study was therefore to evaluate prospectively the clinical potential and correlates of serial CA125 follow-up in an unselected total population with epithelial ovarian cancer. MATERIAL AND METHODS
A total of 651 serum samples were collected prospectively in a longitudinal study from 74 patients with histologically confirmed epithelial ovarian cancer. The 74 consecutive patients attending the centralized gynaecological oncology service in Aberdeen were unselected from the stable population of Grampian. Samples were available from 53 patients prior to definitive staging and cytoreductive surgery. Follow-up samples were obtained from these patients between days 7 and 10 post-operatively, 3 to 4 weekly prior to chemotherapy and at subsequent follow-up (range 3 to 48 months). This accounted for 518 serum samples with a mean of 10 samples per patient (range 1 to 22). Only post-operative and serial follow-up samples were available from the remaining 21 patients. Nine had no evidence of residual disease after primary debulking surgery, whereas 12 had residual or recurrent disease at entry to the study. Patients with FIGO (International Federation of Gynaecologists and Obstetricians) Stage-Ic cancer and above were given platinum-based chemotherapy at 3- to 4-weekly intervals, up to a total of 6 courses, as part of a randomized multi-centre trial. Follow-up was otherwise at 2 to 3 monthly intervals. Intra-operative staging was according to the FIGO classification and histopathological classification and grading of tumours was by World Health Organization (WHO) criteria (Serovet al., 1973). Table I summarizes the stage and histological distribution of the study group, which had a median age of 59 years (range 39 to 79 years). Patients with non-epithelial ovarian malignancies, Krukenberg tumours and tumours of low malignant potential were excluded. Assessment of response to chemotherapy and disease status at follow-up, according to WHO criteria, was by clinical examination, ultrasonography, X-ray-computed tomography and magnetic resonance imaging (WHO, 1979). Those who demonstrated complete (CR) or partial response (PR) were designated responders and those with stable disease (SD), progressive disease (PD) or who died of disease were classified as nonresponders. CA125 assessment of response was defined as progression if, between 2 consecutive samples at least 3 weeks apart, there was more than a 100% increase in CA125 level and if it exceeded 35 U/ml. Regression was defined as a fall of 50% or more in CA125 level, with the original value above 35 U/ml. Neither a 50% fall nor a 100% increase in CA125 level was regarded as equivalent to stable disease. 'To whom correspondence and reprint requests should be addressed. Received: October 22,1991 and in revised form December 10,1991.
59
CA125 RESPONSE IN OVARIAN CANCER TABLE I - STUDY POPULATION, STAGE AND HISTOLOGY DISTRIBUTION (n = 74) Histology
Serous Mu cinous Endometrioid Clear-cell Undifferentiated Total
FIG0 stage I
11
111
IV
Total
7 4 2
3 0 3
17 4 2
3
2
0
3 19
0 8
7 30
8 2 3 0 4 17
35 10 10 5 14 74
TABLE I1 - COMPARISON OF CLINICAL ASSESSMENT AND CA125 ASSESSMENT OF DISEASE STATUS CA125 changes'
Clinical assessment of disease status Regression
Stable
Progression
0 0
1 6 1
14 7 1
Increase Stable Decrease
29
'See text for definition of significant CA125 changes. TABLE III - ABSOLUTE CA125 AND CLINICAL RESPONSE CATEGORY
Serum samples were separated into aliquots and stored at -40°C. They were assayed blind of the clinical data, without being previously thawed. The commercially available kit (CIS UK, London) used to measure serum CA125 was a simultaneous sandwich solid-phase immunoradiometric assay with a sensitivity of 5 U/ml. The inter- and intra-assay co-efficients of variation in our laboratory were 6% and 12% respectively. The CA125 results were not available to influence clinical management. Student's t-test with logarithmic transformation was used to determine statistical significance with the aid of a Minitab package (Statistics Department, Pennsylvania State University, Philadelphia, PA).
Clinical response
CA125 (Uiml) Mean (95% CI)
Complete response (CR) Partial response (PR) Stable or progressive disease (SD or PD)
96l 33-128 1342{98-1681 391'~~ (282-545)
'p < .OOl.-Zp
< 0.05.
RESULTS
Of the 74 study patients, 35 were assessable for clinical response, having evaluable disease after surgery. With a number of these patients relapsing after an initial response or demonstrating a response to second-line treatment, there were 59 observations of clinical response for correlation with changes in antigen level (Table 11). There was 83% concordance between the clinical assessment and marker assessment of response. Rising CAl25 with at least a 100% increase between 2 observations 3 or more weeks apart had a positive predictive value for progressive disease of 0.93. Halving of the CA125 level, on the other hand, had a positive predictive value for disease regression of 0.94. Of the 7 patients with progressive disease and stable CAI25 levels (range 6 to 2,000 U/ml), 6 were in end-stage disease. These apparently false negative CA125 changes will be mentioned again in relation to terminal changes in CA125 prior to death. The 7th patient in this category and the one with a falling CA125 level but with clinically progressive disease went into remission after these observations were made. The absolute CAI25 levels taken during periods of complete response, partial response and stable or progressive disease were also significantly different (Table 111). The 95% confidence interval for CA125 during periods of response (CR or PR) was 37 to 139 Uiml, as compared with 282 to 545 U/ml during periods of no response (SD or PD). During the study, 42 patients died of disease; all had raised CA125 levels at some time during follow-up. Three, however, had CA125 levels < 35 U/ml, 8 to 22 days prior to death. One with brain and pulmonary metastases from an undifferentiated carcinoma had a static CA125 level of 6 U/ml on 5 occasions over the preceding 4 months (pre-chemotherapy level of 147 U/ml). The other 2, with an endometrioid and an undifferentiated carcinoma, had intra-abdominal relapse and a CA125 level of 27 U/ml (preoperative values 287 and 330 U/ml). A falling or static CA125 level was not uncommon over the last 3 months of life. At least 33% of patients (14/42) demonstrated this phenomenon, with up to a 20-fold fall in CA12.5 (4102 to 189 U/ml). Ten of the 12 patients with residual or recurrent disease at entry to the trial had CA125 levels >35 U/ml giving a sensitivity of 83%. The 9 patients with no clinical evidence of disease at recruitment had serum CA125 levels between 6 and
Post-operative time interval (days)
FIGURJ? 1 - Mean CA125 levels with time in responders and non-responders according to residual disease after primary surgery. 0 ,responders, residual disease < 2 crn (n = 11);A,responders, residual disease > 2 cm (n = 7); 0, non-responders, residual disease < 2 cm (n = 6); A, non-responders, residual disease > 2 crn (n = 11). *p < 0.001.
13 U/ml. Two patients relapsed, with changes in CA125 predicting progressive disease in both cases. Figure 1 compares the mean CA125 levels at different time intervals after the primary laparotomy for responders and non-responders stratified according to residual disease. There was a highly significant difference between the values for non-responders with residual disease < 2 cm and responders with residual disease < 2 cm from the time interval 8 to 28 days
60
CRUICKSHANK ETAL.
and thereafter. The values for patients classified as responders with residual disease > 2 cm were significantly different from the values of the 2 previous curves after 29 days. Some patients contributed more than one CA125 value at individual time intervals, while others were not represented in all the time intervals. This was largely due to incomplete data collection. There is no reason, however, to suspect that the missing CA125 samples would markedly affect the results. DISCUSSION
In this prospective, unselected, population-based series, rising or falling CA125 level on serial follow-up correlated with clinically defined disease progression or regression in 49 of 59 instances (83%). There are only 2 other prospective studies which have compared CA125 changes with changes in disease status. Canney et al. (1984) also reported an 83% (19123) concordance between CA125 changes and clinical response. There was, however, no definition for what was regarded as a significant rise or fall in CA125. Altaras et al. (1988) found that the variation in CA125 level reflected clinical response in 88% of cases (36/41), but the assessment of response in this study was not according to recognized international criteria, and CA125 progression required a 50% or greater rise in CAI25 level. Together with the statistically significant difference in absolute CA125 level between observations of complete rcsponse (no evidence of disease), partial response and stable or progressive disease, there is little doubt that serial serum CA125 estimations reflecting tumour burden can be used to objectively monitor the course of disease in individual patients with epithelial ovarian cancer in response to treatment. This is illustrated graphically in Figure 1. Clinical assessment of response in ovarian cancer is notoriously unreliable. Therefore, to use this as the “gold standard” against which changes in CA125 are compared is likely to underestimate the accuracy of CA125 assessment of response. When clinically defined complete response is evaluated at second-look laparotomy, “sub-clinical” disease has been demonstrated in 71% of cases (false negative rate) (Niloff et al., 1985). Indeed, the accuracy of the ultimate test of response in ovarian cancer, i.e., surgical evaluation at second-look laparotomy, is doubtful. The impossibility of excluding residual or distant micrometastases has been illustrated by a relapse rate of at least 25% among patients with complete surgical response (Luesley et al., 1987). In our study there were no patients with rising CA125 at clinical remission, and the one patient with falling CA125 and clinically defined disease progression went into remission after the observation of progression was made, suggesting a false positive clinical assessment. Rising CA125 was predictive of disease progression in 93% of cases, while falling CA125 was predictive of response in 94% of instances. Calculation of these predictive values took no account of the false positives and false negatives in the clinical evaluation of disease status. The superiority of CA125 over the present clinical mcans of detecting residual disease is reflected in the mean CA125 level of 96 Uiml during observations of complete clinical response (Table 111). It appears reasonable to assume that a considerable amount of residual disease is not clinically apparent, and that this accounts for such high CA125 levels (95% confidence interval, 33 to 128 U/ml).
As shown in Table 11, 6 of the 7 patients with progressive disease and stable CA125 levels were in the terminal phase. In clinical practice, these apparently false negative CA125 results would be unlikely to cause confusion when combining serial CA125 follow-up with existing means of monitoring. A falling-off in antigen level prior to death occurred in approximately 25% of patients who died. This observation has been reported in one other patient (Khoo et al., 1987). Again, it is unlikely that such CA125 changes would be misleading in the face of rapidly progressive overwhelming disease. Nevertheless, these 2 phenomena detract from the efficiency of CA125 in the follow-up of ovarian cancer. The Hook effect is a possible explanation of this paradoxical fall in CA125; but serial dilutions revealed that the fall in CA125 levels was real. Another possibility is the formation of CA125-immune complexes, which would mask the detection of antigen in the serum causing an apparent fall in serum CA125. Alternatively, with end-stage disease the anabolic state of the tumour may retain the CA125 antigen as the cell-death rate within the tumour falls and subsequently the release of antigen falls. The antigenic heterogeneity in ovarian cancer is a further possible explanation. The proportion of CA125-expressing cells varies from tumour to tumour (Kabawat et al., 1983). It is also likely that within the same patient the proportion of CA125cxpressing clones varies with time. A change in functional characteristics of the tumour, reflecting resistance prior to death, may be associated with a reduction in the proportion of cells producing CA125, so that, even with rapidly progressive disease, if this involves principally non-CA125-expressing clones, the serum CA125 level will fall. With the information available there is little justification for any clinician involved in the management of patients with ovarian cancer not to use serial CA125 estimations to assess progress, at least in conjunction with existing means of monitoring this condition. Phase-3 studies of first-line cytotoxics in epithelial ovarian cancer have so far been reluctant to recognise clinical decision-making based on serial CA125 follow-up in their protocols. Yet they continue to include clinical assessment of response as the end-point for reporting preliminary results. A working group on tumour-marker criteria has suggested general guidelines for defining tumourmarker response (Bonfrer et al., 1990). An internationally recognized definition of CA125-response criteria is required to allow reliable comparison of reported studies. The time is right for a randomized controlled study to determine whether clinical decision-making based on serial CA125 follow-up has any definitive benefit in terms of outcome, particularly survival, in ovarian cancer. All patients would have serial serum samples for CA125 estimation, but in only half the cases would the CA125 values be available to influence clinical management. ACKNOWLEDGEMENTS
This study was funded by the E.J. Smith executory, Grampian Health Board. CIS UK provided the CA125 kits. We are grateful to Professor A. Klopper for his support and advice. We also thank Mr. B. Duncan and the staff of the Obstetrics and Gynaecology Laboratory, the residents in the gynaecology wards, the nurses at the Joint GynaecologicaliOncology Clinic, and Miss R. Moir, who typed the text.
REFERENCES
ALTARAS, M.M., GOLDBERG, G.L., LEVIN,W., BLOCH,B., DAKGE,L. and SMITH,J., The role of cancer antigen 125 (CA125) in the management of ovarian epithelial carcinomas. Gynecol. Oncol., 30, 26-34-( 1988). ALVAREL, R.D., ALEXANDER, T., BOOTS,L.R., SHINGLETON, H.M., HATCH, K.D., HUBBARD, J., SOONG,S.J. and POTTER,M.E., CA12.5 as
a serum marker for poor prognosis in ovarian malignancies. Gynecol. Oncol., 26,284-289 (1987).
BAST, R.C., KLUG, T., S7 JOHN,E., JENISON,E., NILOFF,J.M., LAZARUS, H., BERKOWITZ, R.S., LEAVITT,T.,GRIFFITHS, C.T., PARKER, L. and ZURAWSKI, V.R., A radioimmunoassay using a monoclonal
CA125 RESPONSE IN OVARIAN CANCER
antibody to monitor the course of epithelial ovarian cancer. New Engl. J. Med., 309,883-887 (1983). BONFRER,J.M.G., CRUICKSHANK, D.J., VAN DALEN,A., FRITSCHE, H.A., HAYES,D.F., JACOBS,I., STAAB,H.J. and ZINDER,O., Working Grou on Tumour Marker Criteria (WGTMC). TumorBioE., 11,287-8 (19907. BRIOSCHI, P.A., IRION,O., BISCHOF,P., BADER,M., FORNI,M. and F., Serum CA125 in epithelial ovarian cancer. A longitudinal KRAUER, study. Brit. J. Obstet. Gynaecol., 94,196-201 (1987). CANNEY,P.A., MOORE, M., WILKINSON, P.M. and JAMES,R.D., Ovarian cancer antigen CA125: a prospective clinical assessment of its role as a tumour marker. Brit. J. Cancer, 50,765-769 (1984). COHEN,G.I., GOLDBERG, J.D., HOLLAND,J.F., BRUCKNER, H.W., DEPPE,G., GUSBERG, S.B., WALLACH, R.C., KABAKOW, B. and RODIN, J., Improved therapy with cisplatin regimes for patients with ovarian carcinoma ( F I G0 stages I11 and IV) as measured by surgical endstaging (second-look operation). Amer. J. Obstet. Gynecol., 145, 955967 (1983). CRUICKSHANK, D.J., FULLERTON, W.T. and KLOPPER, A,, The clinical significance of preoperative serum CA125 in ovarian cancer. Brit. J. Obstet. Gynaecol., 94,692-695 (1987). JOHNSON, R.J., BLACKLEDGE, G., EDDLESTON, B. and CROWTHER, D., Abdominopelvic computed tomography in the management of ovarian carcinoma. Radiology, 146,447 (1983). KABAWAT, S.E., BAST,R.C., WELCH,W.R., KNAPP,R.C. and COLVIN, R.B., Immunopathologic characterisation of a monoclonal antibody that recognises the common surface antigens of human ovarian tumours of serous endometrioid and clear-cell types. Amer. J. clin. Pathol., 79,98-104 (1983). KHOO,S.K., HURST,T., WEBB,M.J., DICKIE,G.J., KEARSLEY, J.H. and MACKAY,E.V., Predictive value of serial CA125 antigen levels in ovarian cancer evaluated by second-look laparotomy. Europ. J. Cancer clin. Oncol., 236, 765-771 (1987). KIVINEN, S., KUOPPALA, T., LEPPILAMPI, M., VUORI, J. and KAUPPILA, A,, Tumour-associated antigen CA125 before and during the treatment of ovarian cancer. Obstet. Gynecol., 67,468-472 (1986).
61
KREBS,H.B., GOPLERUD, D., KILPATRICK, J., MYERS,M.B. and HUNT, A., Role of CA125 as tumor marker in ovarian carcinoma. Obstet. Gynecol., 67,473477 (1986). LAVIN,P.T., KNAPP,R.C., MALKASIAN, G., WHITNEY,C.W., BEREK, J.C. and BAST,R.C., CA125 for the monitoring of ovarian carcinoma during primary therapy. Obstet. Gynecol., 69,223-227 (1987). LI-JUAN,L., XIU-FENG,H., WEN-SHU, L. and A-JU,W., A monoclonal antibody radioimmunoassay for the antigenic determinant CA125 in ovarian cancer patients. Chinese med. J., 99,721-726 (1986). G.R. and LUESLEY, D.M., LAWTON,F.G., CHAN,K.K., BLACKLEDGE, MOULD,J., Second-look laparotomy. In: F. Sharp and W.P. Soutter (eds.), Ovarian cancer+he way ahead. Proceedings of the 17th Study Group of the Royal College of Obstetricians and Gynaecologists in conjunction with the Helene Harris Memorial Trust, pp. 297-309, Royal College of Obstetricians and Gynaecologists, London (1987). NEIJT,J.P., TENBOKKELHUININK, W.W., VANDER BURG,M.E.L., VAN OOSTEROM, A.T., WILLEMSE, P.H.B., HEINTZ,A.P.M., VAN LENT,M., TRIMBOS, J.B., BOUMA,J., VERMORKEN, J.B. and VAN HOUWELINGEN, J.C., Randomised trial comparing two combination chemotherapy regimes (CHAP-5 versus CP) in advanced ovarian carcinoma. J. clin. Oncol., 5,1157 (1987). NILOFF,J.M., BAST,R.C., SCHAETZL, E.M. and KNAPP,R.C., Predictive value of CA125 antigen levels in second-look procedures for ovarian cancer. Amer. J. Obstet. Gynecol., 151,981-986 (1985). SEROV,S.F., SCULLY, R.E. and SOBIN,L.H., International histological classification of tumours, 9. Histological typing of ovarian tumours. WHO, Geneva (1973). SEVELDA, P., SALZER,H., DITTRICH,C., PATEISKY, N. and SPONA,J., The diagnostic validity of the tumour marker CA125 in ovarian cancer patients. TumorDiugn. Therap., 8,115-120 (1987). VERGOTE, I.B., B0RMER, O.P. and ABELER,V.M., Evaluation of serum CA125 levels in the monitoring of ovarian cancer. Amer. J. Obstet. Gynecol., 157,88-92 (1987). WORLDHEALTHORGANIZATION, WHO Handbook for reporting results of cancer treatment, 48. WHO Offset Publications, Geneva (1979).
Publication of the International Union Against Cancer Publicationde I'Union lnternationale Contre le Cancer
CA125-RESPONSE ASSESSMENT IN EPITHELIAL OVARIAN CANCER D.J. CRUICKSHANK', P.B. TERRYand W.T. FULLERTON Department of Obstetrics and Gynaecology, University of Aberdeen, Royal Infirmary, Aberdeen AB9 2ZB, Scotland. To assess the clinical potentialof serial serum CAI 25 measurements in the follow-up of patients with epithelial ovarian cancer, 74 consecutive unselected patients with histologically confirmed ovarian carcinomawere studied prospectively. There was an 83Oh concordance between clinical assessment and CAI 25 assessmentof response. The positive predictivevalues of a rising CA I25 for disease progression and a falling CA I25 for disease regression were 0.93 and 0.94, respectively. The absolute CAI 25 values during observations of complete response (mean 96 U/ml; 95% confidence interval; 33 to 128 U/ml), partial response (mean 134 U/ml; 95% confidence interval; 98 to I59 U/ml) and stable or progressive disease (mean 39 I U/ml; 95% confidence interval; 282 to 545 U/ml) were significantly different. A randomized study is required to determine whether CAI25 monitoring has any benefit in terms of outcome, and particularlysurvival, in epithelial ovarian cancer.
Epithelial ovarian cancer is an insidious disease which spreads locally in the pelvis and diffusely over the peritoneal surfaces of the abdominal contents. As a result, monitoring of disease status in response to chemotherapy after surgery, using standard imaging techniques (ultrasound, computerized axial tomography and magnetic resonance imaging), is unreliable. It has been suggested that computerized axial tomography is the most informative non-invasive method for monitoring response (Johnson et al., 1983). However, the sensitivity of this test depends not only on the size of the residual or recurrent disease but also on its site. In addition, it is an expensive and impractical means of monthly response evaluation. The pressure for surgical response data in phase-3 studies highlights the deficiencies in the clinical assessment of response (Cohen et al., 1983). If the combination of cis-platinum and cyclophosphamide produccs a 74% response rate, then 26% of patients with advanced disease will be resistant to treatment (Neijt et al., 1987). Nevertheless, it is unusual for patients to be withdrawn from phase-3 studies because of progressive disease on treatment, the reason being the extent of non-evaluable or nonmeasurable residual disease (up to 80%) after cytoreductive surgery which is unsuitable for monitoring by standard imaging modalities. Resistant small-volume rcsidual disease progresses unnoticed during treatment. The 17th Study Group of the Royal College of Obstetricians and Gynaecologists stated that a major priority was the development of reliable methods of monitoring patients being treated for ovarian cancer. The antigenic determinant CA125 has been extensively studied in epithelial ovarian cancer. Pre-operative serum levels correlate with tumour load and all epithelial sub-types are associated with elevated levels (Cruickshank et al., 1987). The sensitivity of CA125 in ovarian cancer is over 80% in most published series (Cruickshank et al., 1987; Bast et al., 1983; Canney et al., 1984; Kivinen et al., 1986; Li-juan et al., 3986; Krebs et al., 1986; Alvarez et al., 1987; Vergote et al., 1987; Lavin et aL, 1987; Sevelda et al., 1987; Brioschi et al., 1987; Altaras et al., 1988). There is great difficulty, however, in interpreting and comparing the majority of these studies. They are largely retrospective, using stored serum banks. Most populations studied are patients with advanced disease and are dependent on oncology referral patterns, with a bias for bulky residual disease or recurrent disease. Such biases would tend to present CA12.5 in a favourable light. Some studics exclude mucinous carcinomas, while others include tumours of low malignant potential or indeed non-epithelial ovarian
cancers. There is also the problem of quality control, with different commercially available CA125 kits and assay methods being used by different workers. With particular reference to monitoring, most studies fail to define significant CA125 changes or response criteria, and many do not use internationally accepted criteria for clinical response assessment (World Health Organization, 1979). The aim of this study was therefore to evaluate prospectively the clinical potential and correlates of serial CA125 follow-up in an unselected total population with epithelial ovarian cancer. MATERIAL AND METHODS
A total of 651 serum samples were collected prospectively in a longitudinal study from 74 patients with histologically confirmed epithelial ovarian cancer. The 74 consecutive patients attending the centralized gynaecological oncology service in Aberdeen were unselected from the stable population of Grampian. Samples were available from 53 patients prior to definitive staging and cytoreductive surgery. Follow-up samples were obtained from these patients between days 7 and 10 post-operatively, 3 to 4 weekly prior to chemotherapy and at subsequent follow-up (range 3 to 48 months). This accounted for 518 serum samples with a mean of 10 samples per patient (range 1 to 22). Only post-operative and serial follow-up samples were available from the remaining 21 patients. Nine had no evidence of residual disease after primary debulking surgery, whereas 12 had residual or recurrent disease at entry to the study. Patients with FIGO (International Federation of Gynaecologists and Obstetricians) Stage-Ic cancer and above were given platinum-based chemotherapy at 3- to 4-weekly intervals, up to a total of 6 courses, as part of a randomized multi-centre trial. Follow-up was otherwise at 2 to 3 monthly intervals. Intra-operative staging was according to the FIGO classification and histopathological classification and grading of tumours was by World Health Organization (WHO) criteria (Serovet al., 1973). Table I summarizes the stage and histological distribution of the study group, which had a median age of 59 years (range 39 to 79 years). Patients with non-epithelial ovarian malignancies, Krukenberg tumours and tumours of low malignant potential were excluded. Assessment of response to chemotherapy and disease status at follow-up, according to WHO criteria, was by clinical examination, ultrasonography, X-ray-computed tomography and magnetic resonance imaging (WHO, 1979). Those who demonstrated complete (CR) or partial response (PR) were designated responders and those with stable disease (SD), progressive disease (PD) or who died of disease were classified as nonresponders. CA125 assessment of response was defined as progression if, between 2 consecutive samples at least 3 weeks apart, there was more than a 100% increase in CA125 level and if it exceeded 35 U/ml. Regression was defined as a fall of 50% or more in CA125 level, with the original value above 35 U/ml. Neither a 50% fall nor a 100% increase in CA125 level was regarded as equivalent to stable disease. 'To whom correspondence and reprint requests should be addressed. Received: October 22,1991 and in revised form December 10,1991.
59
CA125 RESPONSE IN OVARIAN CANCER TABLE I - STUDY POPULATION, STAGE AND HISTOLOGY DISTRIBUTION (n = 74) Histology
Serous Mu cinous Endometrioid Clear-cell Undifferentiated Total
FIG0 stage I
11
111
IV
Total
7 4 2
3 0 3
17 4 2
3
2
0
3 19
0 8
7 30
8 2 3 0 4 17
35 10 10 5 14 74
TABLE I1 - COMPARISON OF CLINICAL ASSESSMENT AND CA125 ASSESSMENT OF DISEASE STATUS CA125 changes'
Clinical assessment of disease status Regression
Stable
Progression
0 0
1 6 1
14 7 1
Increase Stable Decrease
29
'See text for definition of significant CA125 changes. TABLE III - ABSOLUTE CA125 AND CLINICAL RESPONSE CATEGORY
Serum samples were separated into aliquots and stored at -40°C. They were assayed blind of the clinical data, without being previously thawed. The commercially available kit (CIS UK, London) used to measure serum CA125 was a simultaneous sandwich solid-phase immunoradiometric assay with a sensitivity of 5 U/ml. The inter- and intra-assay co-efficients of variation in our laboratory were 6% and 12% respectively. The CA125 results were not available to influence clinical management. Student's t-test with logarithmic transformation was used to determine statistical significance with the aid of a Minitab package (Statistics Department, Pennsylvania State University, Philadelphia, PA).
Clinical response
CA125 (Uiml) Mean (95% CI)
Complete response (CR) Partial response (PR) Stable or progressive disease (SD or PD)
96l 33-128 1342{98-1681 391'~~ (282-545)
'p < .OOl.-Zp
< 0.05.
RESULTS
Of the 74 study patients, 35 were assessable for clinical response, having evaluable disease after surgery. With a number of these patients relapsing after an initial response or demonstrating a response to second-line treatment, there were 59 observations of clinical response for correlation with changes in antigen level (Table 11). There was 83% concordance between the clinical assessment and marker assessment of response. Rising CAl25 with at least a 100% increase between 2 observations 3 or more weeks apart had a positive predictive value for progressive disease of 0.93. Halving of the CA125 level, on the other hand, had a positive predictive value for disease regression of 0.94. Of the 7 patients with progressive disease and stable CAI25 levels (range 6 to 2,000 U/ml), 6 were in end-stage disease. These apparently false negative CA125 changes will be mentioned again in relation to terminal changes in CA125 prior to death. The 7th patient in this category and the one with a falling CA125 level but with clinically progressive disease went into remission after these observations were made. The absolute CAI25 levels taken during periods of complete response, partial response and stable or progressive disease were also significantly different (Table 111). The 95% confidence interval for CA125 during periods of response (CR or PR) was 37 to 139 Uiml, as compared with 282 to 545 U/ml during periods of no response (SD or PD). During the study, 42 patients died of disease; all had raised CA125 levels at some time during follow-up. Three, however, had CA125 levels < 35 U/ml, 8 to 22 days prior to death. One with brain and pulmonary metastases from an undifferentiated carcinoma had a static CA125 level of 6 U/ml on 5 occasions over the preceding 4 months (pre-chemotherapy level of 147 U/ml). The other 2, with an endometrioid and an undifferentiated carcinoma, had intra-abdominal relapse and a CA125 level of 27 U/ml (preoperative values 287 and 330 U/ml). A falling or static CA125 level was not uncommon over the last 3 months of life. At least 33% of patients (14/42) demonstrated this phenomenon, with up to a 20-fold fall in CA12.5 (4102 to 189 U/ml). Ten of the 12 patients with residual or recurrent disease at entry to the trial had CA125 levels >35 U/ml giving a sensitivity of 83%. The 9 patients with no clinical evidence of disease at recruitment had serum CA125 levels between 6 and
Post-operative time interval (days)
FIGURJ? 1 - Mean CA125 levels with time in responders and non-responders according to residual disease after primary surgery. 0 ,responders, residual disease < 2 crn (n = 11);A,responders, residual disease > 2 cm (n = 7); 0, non-responders, residual disease < 2 cm (n = 6); A, non-responders, residual disease > 2 crn (n = 11). *p < 0.001.
13 U/ml. Two patients relapsed, with changes in CA125 predicting progressive disease in both cases. Figure 1 compares the mean CA125 levels at different time intervals after the primary laparotomy for responders and non-responders stratified according to residual disease. There was a highly significant difference between the values for non-responders with residual disease < 2 cm and responders with residual disease < 2 cm from the time interval 8 to 28 days
60
CRUICKSHANK ETAL.
and thereafter. The values for patients classified as responders with residual disease > 2 cm were significantly different from the values of the 2 previous curves after 29 days. Some patients contributed more than one CA125 value at individual time intervals, while others were not represented in all the time intervals. This was largely due to incomplete data collection. There is no reason, however, to suspect that the missing CA125 samples would markedly affect the results. DISCUSSION
In this prospective, unselected, population-based series, rising or falling CA125 level on serial follow-up correlated with clinically defined disease progression or regression in 49 of 59 instances (83%). There are only 2 other prospective studies which have compared CA125 changes with changes in disease status. Canney et al. (1984) also reported an 83% (19123) concordance between CA125 changes and clinical response. There was, however, no definition for what was regarded as a significant rise or fall in CA125. Altaras et al. (1988) found that the variation in CA125 level reflected clinical response in 88% of cases (36/41), but the assessment of response in this study was not according to recognized international criteria, and CA125 progression required a 50% or greater rise in CAI25 level. Together with the statistically significant difference in absolute CA125 level between observations of complete rcsponse (no evidence of disease), partial response and stable or progressive disease, there is little doubt that serial serum CA125 estimations reflecting tumour burden can be used to objectively monitor the course of disease in individual patients with epithelial ovarian cancer in response to treatment. This is illustrated graphically in Figure 1. Clinical assessment of response in ovarian cancer is notoriously unreliable. Therefore, to use this as the “gold standard” against which changes in CA125 are compared is likely to underestimate the accuracy of CA125 assessment of response. When clinically defined complete response is evaluated at second-look laparotomy, “sub-clinical” disease has been demonstrated in 71% of cases (false negative rate) (Niloff et al., 1985). Indeed, the accuracy of the ultimate test of response in ovarian cancer, i.e., surgical evaluation at second-look laparotomy, is doubtful. The impossibility of excluding residual or distant micrometastases has been illustrated by a relapse rate of at least 25% among patients with complete surgical response (Luesley et al., 1987). In our study there were no patients with rising CA125 at clinical remission, and the one patient with falling CA125 and clinically defined disease progression went into remission after the observation of progression was made, suggesting a false positive clinical assessment. Rising CA125 was predictive of disease progression in 93% of cases, while falling CA125 was predictive of response in 94% of instances. Calculation of these predictive values took no account of the false positives and false negatives in the clinical evaluation of disease status. The superiority of CA125 over the present clinical mcans of detecting residual disease is reflected in the mean CA125 level of 96 Uiml during observations of complete clinical response (Table 111). It appears reasonable to assume that a considerable amount of residual disease is not clinically apparent, and that this accounts for such high CA125 levels (95% confidence interval, 33 to 128 U/ml).
As shown in Table 11, 6 of the 7 patients with progressive disease and stable CA125 levels were in the terminal phase. In clinical practice, these apparently false negative CA125 results would be unlikely to cause confusion when combining serial CA125 follow-up with existing means of monitoring. A falling-off in antigen level prior to death occurred in approximately 25% of patients who died. This observation has been reported in one other patient (Khoo et al., 1987). Again, it is unlikely that such CA125 changes would be misleading in the face of rapidly progressive overwhelming disease. Nevertheless, these 2 phenomena detract from the efficiency of CA125 in the follow-up of ovarian cancer. The Hook effect is a possible explanation of this paradoxical fall in CA125; but serial dilutions revealed that the fall in CA125 levels was real. Another possibility is the formation of CA125-immune complexes, which would mask the detection of antigen in the serum causing an apparent fall in serum CA125. Alternatively, with end-stage disease the anabolic state of the tumour may retain the CA125 antigen as the cell-death rate within the tumour falls and subsequently the release of antigen falls. The antigenic heterogeneity in ovarian cancer is a further possible explanation. The proportion of CA125-expressing cells varies from tumour to tumour (Kabawat et al., 1983). It is also likely that within the same patient the proportion of CA125cxpressing clones varies with time. A change in functional characteristics of the tumour, reflecting resistance prior to death, may be associated with a reduction in the proportion of cells producing CA125, so that, even with rapidly progressive disease, if this involves principally non-CA125-expressing clones, the serum CA125 level will fall. With the information available there is little justification for any clinician involved in the management of patients with ovarian cancer not to use serial CA125 estimations to assess progress, at least in conjunction with existing means of monitoring this condition. Phase-3 studies of first-line cytotoxics in epithelial ovarian cancer have so far been reluctant to recognise clinical decision-making based on serial CA125 follow-up in their protocols. Yet they continue to include clinical assessment of response as the end-point for reporting preliminary results. A working group on tumour-marker criteria has suggested general guidelines for defining tumourmarker response (Bonfrer et al., 1990). An internationally recognized definition of CA125-response criteria is required to allow reliable comparison of reported studies. The time is right for a randomized controlled study to determine whether clinical decision-making based on serial CA125 follow-up has any definitive benefit in terms of outcome, particularly survival, in ovarian cancer. All patients would have serial serum samples for CA125 estimation, but in only half the cases would the CA125 values be available to influence clinical management. ACKNOWLEDGEMENTS
This study was funded by the E.J. Smith executory, Grampian Health Board. CIS UK provided the CA125 kits. We are grateful to Professor A. Klopper for his support and advice. We also thank Mr. B. Duncan and the staff of the Obstetrics and Gynaecology Laboratory, the residents in the gynaecology wards, the nurses at the Joint GynaecologicaliOncology Clinic, and Miss R. Moir, who typed the text.
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