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Tumor antigen CA 125 as a marker of ovarian epithelial carcinoma
CVNECOLOrlC ONCOLO~V 28, 61--67 (1987)
Tumor Antigen CA 125 as a Marker of Ovarian Epithelial Carcinoma F. ZANABONI,* F. VERCADORO,* M. PRESTI,* P. GALLO~TI,? F. LOMBARDI,$ AND G. BoLls* "111Department of Obstetrics and Gynecology, University of Milan, Italy, ?Department of lnternal Medicine, Hospital of Vigevano (PV), Italy, and CDepartment of lnternal Medicine, Hospital of Magenta (MI), Italy Received April 1, 1986 Serum CA 125 was measured in 100 patients with ovarian epithelial carcinoma at diagnosis and in follow-up. Levels over 35 U / m l were found in 43 (75.4%) of 57 cases at diagnosis and in 21 (48.8%) of 43 c a s e s in follow-up. A correlation was found between tumor burden and m a r k e r positivity: a d v a n c e d Stages (III and IV) and recurrences had 84.2 and 91% o f positivity, c o m p a r e d to 59,1% in early disease (Stages I and II). Analysis by histotype and F I G O grade revealed a difference between the mucinous type and the others and a positive association with less differentiated tumors. In the 30 patients submitted to secondlook laparotomy a correlation was found between CA 125 levels and pathological r e s p o n s e in 86.7% of cases. This ovarian cancer m a r k e r may thus be more useful in monitoring the r e s p o n s e to t r e a t m e n t and in long-term follow-up than in diagnosis. © 1987 Academic Press, Inc.
INTRODUCTION During the last 20 years tumor-associated antigens have been widely investigated from many angles, including their relation to ovarian epithelial cancers [1-3]. To date the most sensitive and specific antibody raised against these surface structures is the routine I g G 1 0 C 125, which recognizes the antigenic determinant CA 125, associated with ovarian epithelial carcinomas [4-8]. A radioimmunoassay with OC 125 can be used to monitor serum levels of the antigen in patients with early or advanced disease. MATERIAL AND METHODS Patients. From April 1984 to January 1986 serum samples collected from 100 patients (median age 56 years) with histological diagnosis of ovarian epithelial carcinoma were cryopreserved at the III Department of Obstetrics and Gynecology, University of Milan. Details of the case list are given in Table 1. The samples were obtained at diagnosis (when possible) and monthly during subsequent therapy or follow-up, for a minimum period of 3 months and a maximum of 21 months. At the time of diagnosis 28 patients were FIGO Stage I, 7 Stage II, 60 Stage III, and 5 Stage IV. Histologically 45 tumors were serous, 10 mucinous, 17 61 0090-8258/87 $1.50
Copyright © 1987by AcademicPress, Inc. All rightsof reproduction in any form reserved.
62
ZANABONI ET AL. TABLE 1 CHARACTERISTICS OF PATIENTS (N = 100) MONITORED WITH THE OC 125 ASSAY Stage I II III IV Histotype Serous Mucinous Endometrioid Clear cell Mixed Undifferentiated Grade 1 2 3
28 7 60 5 45 10 17 13 12 3 21 39 40
endometrioid, 13 clear cell, 12 mixed, and 3 undifferentiated. The least-differentiated tumors (G2-G3) were the largest group (Table 1). Judgment of disease state (progression/stability/regression) was based on objective intraoperative observation of tumor masses, on serial observations of palpable nodules, on serial chest roentgenograms and computerized tomography, or ultrasound analysis of retroperitoneal nodes. Regression of disease was considered a >50% reduction in the size of all detectable lesions. Progression was the appearance of new lesions or a 25% increase in previously detected tumor nodules. Clinical condition and marker assessment of disease state were correlated for all patients. All the Stage III or IV patients clinically considered in complete or partial response underwent a second-look laparotomy at the end of 5 or 6 cycles of chemotherapy. Currently, a correlation has been established in 30 patients between antigen levels and the pathological response found on second-look. CA 125 assay. The immunoradiometric assay utilizes the purified OC 125 monoclonal antibody on a solid-phase immunoadsorbent to bind the CA 125 in 100 t~l of serum. The bound antigen can be detected by simultaneous incubation with 125I-labeled OC 125, as described [6,8]. CA 125 amounts are expressed in arbitrary units, based on comparison with standard controls. Clinical studies described in the literature [4,5], confirmed by our curves, consider values under 35 U/ml as normal; only 1% of healthy donors have higher levels. We therefore considered as positive only antigen levels higher than this threshold. Statistical analysis. To evaluate the association between stage, histotype, grade, and the presence of the marker we used a multiple logistic model. This measures the association of each of the above independent variables with the dependent variable (presence/absence of the marker), accounting simultaneously for their interrelations.
63
CA 125 IN OVARIAN CARCINOMA TABLE 2 CORRELATION BETWEEN STAGE, HISTOTYPE, GRADE, AND C A 125 LEVELS C A 125 Levels Pos. (%)
Neg. (%)
RR (CI)"
Total (79)
1.0b 0.64 (0.06 - 6.73) 3.42 (0.89 - 13.06) 1.65 (0.11 - 24.47)
17 5 53 4
Stage I II III IV
Histotype Serous Endometrioid Clear Cell Mixed Undiff. Mucinous Grade 1 2 3
9 4 47 3
(52.9) (80) (88.7) (75)
8 1 6 1
(47.4) (20) (11.3) (25)
30 (81.1) 10 (76.9) 9 (81.8) 11 (100) 2 (66.7) 1 (25)
7 (18.9) 3 (23.1) 2 (18.2) -1 (33.3) 3 (75)
0.15 (0.01 -
1.95)
37 13 11 11 3 4
6 (42.8) 27 (93.1) 30 (83.3)
8 (57.1) 2 (6.9) 6 (16.7)
1.0 b 9.71 (1.69 - 57.71) 1.52 (0.35 - 6.58)
14 29 36
1.0 b
a RR = Relative risk; CI = confidence interval.
b Reference category.
The results of analysis are expressed, for each category of variables considered, in terms of RR (relative risk), i.e., the chance of finding the marker relative to an arbitrarily defined reference category, for which the RR is, of course, one. In this study the reference categories were Stage I, Grade I, and all the nonmucinous histotypes. Each RR is associated with its confidence interval (CI) at the 0.95 level, which shows the statistical significance of the association (i.e., P < 0.05 if the value 1.0 does not fall within the confidence interval). RESULTS
CA 125 levels over 35 U/ml were found in 43/57 patients at diagnosis (75.4%) and in 21/43 patients in follow-up (48.8%). CA 125 Levels and FIGO Stage As shown in Table 2, we analyzed 79 cases with tumor masses potentially producing the marker before surgery (57) or at recurrence (22). In the 57 patients with a serum sample at diagnosis we found 53.3% (8/15) of positivity for Stage I, 75% (3/4) for Stage II, 85.3% (29/34) for Stage III, and 75% (3/4) for Stage IV. This good correlation was confirmed in patients with recurrence, 90.9% (20/22) of whom had high levels of the marker.
64
ZANABONI ET AL. TABLE 3 CORRELATION BETWEEN SURGICAL DISEASE STATE EVALUATION AND CA 125 LEVELS CA 125 Levels
Pathological response a
Neg. (%)
Pos. (%)
CR PR NC Relapse b
15 (88.2) 2 (25) ---
2 6 2 3b
(11.8) (75) (I00) (100)
Total patients (30) 17 8 2 3
CR = Complete response; PR = partial response; NC = no change. b Patients in clinical complete response submitted to third-look laparotomy because of a stable elevation of serum CA 125.
A large number of the 79 patients analyzed had a histological diagnosis of ovarian serous cystoadenocarcinoma (46.8%). Marker levels were positive in 81.1% of these cases. Table 2 shows the relationship between histotype and antigen values. Our results are similar to those collected by others [5] and confirm the difference in the expression of the marker between the mucinous type and the others.
CA 125 Levels and Histological Grade Table 2 shows the results of analysis of the FIGO tumor grading. The percentage of positivity was larger in cases with less-differentiated tumors. Multiple logistic analysis of the three variables, stage, histotype, and grade, indicated that only Grade 2 seemed to be associated with the presence of the marker at a statistically significant level (P < 0.05). This is probably because some categories were poorly represented in this case list.
CA 125 Levels and Pathological Response At the end of five or six courses of chemotherapy, our protocols for advanced ovarian epithelial tumors include an objective intraoperative assessment of the response. Eligible for this second-look laparotomy are all patients considered in clinical complete response (CR = absence of disease) and those in clinical partial response (PR = reduction >50%). In January 1986, 30 patients with previously positive multiple samples of the tumor marker underwent this procedure. Table 3 shows the antigen levels and the pathological response, which were in agreement in 86.7% (26/30) of the cases. A negative value was associated with CR in 88.2% of the cases (15/17). In the PRs the surgical finding was related to the marker value in 75% (6/8); the two patients with negative levels had a microscopic residual tumor (patient 1) and only a vaginal nodule (patient 2). The marker was stable or increased in all five cases of stable disease (NC = no change) or relapse. We included here three patients who, being in follow-up after a CR, were undergoing third-look laparotomy because of a rise in the serum
65
CA 125 IN OVARIAN CARCINOMA TABLE 4 CLINICAL COURSE OF SIX PATIENTS WITH CA 125 ELEVATIONDURING FOLLOW-UP
Patient No.
Relapse
Time to relapse (months)
1 2 3 4 5 6
Aortic nodes Lung + liver Bowel Pelvis Vagina Pelvic peritoneum
14 5 12 1 1.5 3.5
antigen. They showed relapses in sites not reached clinically (Table 4, patients 1, 3, and 6). DISCUSSION During the last 2 decades one of the pathologist's major aims has been to discover a marker of ovarian epithelial tumors to improve treatment of this complex disease. The antigenic determinant CA 125, found by Bast, offered new prospects, especially in the long-term control of these cancers [4-8]. As reported in the literature, we found 75.4% cases positive (>35 U/ml) at diagnosis. This was in excellent correlation with the tumor burden at the time of sampling. In the advanced forms (Stages II1 and IV) the marker was present in 84.2% (32/38), compared with 57.9% (11/19) of the early cases (Stages I and 1I). Of the 43 patients for whom baseline value at diagnosis was not available, obviously fewer had positive levels (23/43). Among these patients in follow-up, 91% (20/22) of the recurrences had high marker. Until now, only 6 of these cases presented a rise in serum CA 125 before clinical relapse. Conceivably, therefore, CA 125 is produced slowly by tumors sensitive to antineoplastic drugs; in recurrences there could be a selection of cell clones with different metabolic activity, resulting in lower expression of the antigen. Considering the CA 125 levels in relation to histotype and grading, our findings are similar to those published so far: The mucinous type seems to differ from the others, producing less antigen. Unfortunately, despite the undeniable trend, the number of cases of this category was too small to reach statistical significance. An interesting finding was the correlation between the grade of differentiation of a tumor and its inversely proportional capacity to express positive serum levels of the marker. Statistical analysis found a close association with the presence of CA 125 only for Grade 2. The use of the marker in following the response during treatment was also interesting, as mentioned by Bast et al. [9]. The present study found a good correlation between the clinical outcome and CA 125 levels. A drop in antigen level was almost always associated with clinical remission, whereas a plateau or a rise accompanied a therapeutic failure. Of the 27 patients submitted to second-look laparotomy after five or six courses
66
ZANABONI ET AL.
of chemotherapy for advanced cancer, 25 were found to be in CR or PR. There were only two false negatives among the eight PRs. These very promising findings suggest it is still too soon to give up an invasive technique like second-look laparotomy. In fact CA 125 was not detectable when the tumor burden was microscopic, as in 1 of these 2 cases. This limit could be improved in the future with a more purified antibody and better sensitivity of the system. The presence of false positives in the CR series is very important, as a high marker level is a further incitement for the surgeon to take multiple random biopsies during an apparently negative second-look. We know, in fact, that there will be a recurrence in 25-30% of patients with a negative second-look. Only the long-term follow-up of these two patients in CR with positive CA 125 will tell us whether they were cases of false-positive marker or false-negative pathological response. Finally, it is interesting to note the predictive value of this assay in the followup of patients in CR (Stages III and IV) and in the early stages. In our series, high CA 125 levels preceded a clinical recurrence in six cases (Table 4). Instructive was the fact that three of these patients had relapses in sites not easily detectable by the usual gynecological examination. Their tumor recurrence was found on third-look laparotomy, made in the light of persistently high marker levels. CA 125 may, therefore, sometimes be a predictor of relapse in asymptomatic patients. We suggest, however, that at least two high values should be found before suspicion is aroused, in order to avoid false positives due to metabolic problems. At our present stage of knowledge, it is not justified to start antitumoral treatment in a patient in CR only on the basis of an increase in the marker, not documented by histological diagnosis of relapse. The goal of gynecological oncologists is to support clinical follow-up with a sensitive and specific marker useful in ovarian cancer, as has proved possible for trophoblastic disease and germinal tumors. Until the present time the only possible check of disease state in ovarian epithelial cancer was surgical laparoscopy or laparotomy. Unfortunately, we are still far from applying this marker in population screening; the lack of specificity of the tumor-associated antigens known to date, including CA 125 [10], precludes their introduction in a prevention system.
ACKNOWLEDGMENTS We are grateful to Dr. G. Valsecchi and Dr. A. Decarli (Biostatistics Institute, University of Milan) for their precious statistical advice.
REFERENCES 1. Knauf, S., and Urbach, G. I. A study of ovarian cancer patients using a radioimmunoassay for human ovarian tumor-associated antigen OCA, Amer. J. Obstet. Gynecol. 138, 1222-1223 (1980). 2. Battacharya, M., and Barlow, J. J. Ovarian cystoadenocarcinoma associated antigen (OCAA), in Compendium of Assays for Immunodiagnosis of Human Cancer (R. B. Herberman, Ed~), Elsevier, New York, pp. 527-531 (1979). 3. Del Villano, B. C., Brennan, S., Brock, P., Bucher, C., Liu, V., McClure, M., Rake, B., Space, S., Westrick, B., Shoemaker, H., and Zurawski, V., Jr. Radioimmunometric assay for a monoclonal antibody-defined tumor marker, CA 19-9, Clin. Chem. 29, 549-552 (1983).
CA 125 IN OVARIAN CARCINOMA
67
4. Bast, R. C., Jr., Feeney, M., Lazarus, H., Nadler, L. M., Colvin, R, B., and Knapp, R. C. Reactivity of a monoclonal antibody with human ovarian carcinoma, J. Clin. Invest. 68, 13311337 (1981). 5. Kabawat, S. E., Bast, R. C., Jr., Welch, W. R., Knapp, R. C., and Colvin, R. B. Immunopathologic characterization of a monoclonal antibody that recognizes common surface antigens on human ovarian tumors of serous, endometrioid, and clear-cell types, Amer. J. Clin. Pathol. 79, 98104 (1983). 6. Bast, R. C., Jr., Klug, T. L., St. John, E., Jenison, E., Niloff, J. M., Lazarus, H., Berkowitz, R. S., Leavitt, T., Griffiths, C. T., Parker, L., Zurawski, V. R., and Knapp, R. C. A radioimmunoassay using a monoclonal antibody to monitor the course of epithelial ovarian cancer, N. Engl. J. Med. 309, 883-887 (1983). 7. Bast, R. C., Jr., Klug, T. L., Schaetzl, E., Lavin, P., Niloff, J. M., Greber, T. F., Zurawski, V. R., Jr., and Knapp, R. C. Monitoring human ovarian carcinoma with a combination of CA 125, CA 19-9, and CEA, Amer. J. Obstet. Gynecol. 149, 553-559 (1984). 8. Klug, T. L., Bast, R. C., Jr., Niloff, J. M., Knapp, R. C., and Zurawski~ V. R., Jr. A monoclonal antibody immunoradiometric assay for an antigenic determinant (CA 125) associated with human epithelial ovarian carcinomas, Cancer Res. 44, 1048-1053 (1984). 9. Niloff, J. M., Bast, R. C., Jr., Schaetzl, E. M., and Knapp, R. C. Predictive value of CA 125 antigen levels in second-look procedures for ovarian cancer, Amer. J. Obstet. Gynecol. 151, 981-986 (1985). 10. Niloff, J. M., Klug, T. L., Schaetzl, E. M., Zurawski, V. R., Knapp, R. C., and Bast, R. C., Jr. Elevation of serum CA 125 in carcinomas of the fallopian tube, endometrium, and endocervix, Amer. J. Obstet. Gynecol. 148, 1057-1058 (1984).
Tumor Antigen CA 125 as a Marker of Ovarian Epithelial Carcinoma F. ZANABONI,* F. VERCADORO,* M. PRESTI,* P. GALLO~TI,? F. LOMBARDI,$ AND G. BoLls* "111Department of Obstetrics and Gynecology, University of Milan, Italy, ?Department of lnternal Medicine, Hospital of Vigevano (PV), Italy, and CDepartment of lnternal Medicine, Hospital of Magenta (MI), Italy Received April 1, 1986 Serum CA 125 was measured in 100 patients with ovarian epithelial carcinoma at diagnosis and in follow-up. Levels over 35 U / m l were found in 43 (75.4%) of 57 cases at diagnosis and in 21 (48.8%) of 43 c a s e s in follow-up. A correlation was found between tumor burden and m a r k e r positivity: a d v a n c e d Stages (III and IV) and recurrences had 84.2 and 91% o f positivity, c o m p a r e d to 59,1% in early disease (Stages I and II). Analysis by histotype and F I G O grade revealed a difference between the mucinous type and the others and a positive association with less differentiated tumors. In the 30 patients submitted to secondlook laparotomy a correlation was found between CA 125 levels and pathological r e s p o n s e in 86.7% of cases. This ovarian cancer m a r k e r may thus be more useful in monitoring the r e s p o n s e to t r e a t m e n t and in long-term follow-up than in diagnosis. © 1987 Academic Press, Inc.
INTRODUCTION During the last 20 years tumor-associated antigens have been widely investigated from many angles, including their relation to ovarian epithelial cancers [1-3]. To date the most sensitive and specific antibody raised against these surface structures is the routine I g G 1 0 C 125, which recognizes the antigenic determinant CA 125, associated with ovarian epithelial carcinomas [4-8]. A radioimmunoassay with OC 125 can be used to monitor serum levels of the antigen in patients with early or advanced disease. MATERIAL AND METHODS Patients. From April 1984 to January 1986 serum samples collected from 100 patients (median age 56 years) with histological diagnosis of ovarian epithelial carcinoma were cryopreserved at the III Department of Obstetrics and Gynecology, University of Milan. Details of the case list are given in Table 1. The samples were obtained at diagnosis (when possible) and monthly during subsequent therapy or follow-up, for a minimum period of 3 months and a maximum of 21 months. At the time of diagnosis 28 patients were FIGO Stage I, 7 Stage II, 60 Stage III, and 5 Stage IV. Histologically 45 tumors were serous, 10 mucinous, 17 61 0090-8258/87 $1.50
Copyright © 1987by AcademicPress, Inc. All rightsof reproduction in any form reserved.
62
ZANABONI ET AL. TABLE 1 CHARACTERISTICS OF PATIENTS (N = 100) MONITORED WITH THE OC 125 ASSAY Stage I II III IV Histotype Serous Mucinous Endometrioid Clear cell Mixed Undifferentiated Grade 1 2 3
28 7 60 5 45 10 17 13 12 3 21 39 40
endometrioid, 13 clear cell, 12 mixed, and 3 undifferentiated. The least-differentiated tumors (G2-G3) were the largest group (Table 1). Judgment of disease state (progression/stability/regression) was based on objective intraoperative observation of tumor masses, on serial observations of palpable nodules, on serial chest roentgenograms and computerized tomography, or ultrasound analysis of retroperitoneal nodes. Regression of disease was considered a >50% reduction in the size of all detectable lesions. Progression was the appearance of new lesions or a 25% increase in previously detected tumor nodules. Clinical condition and marker assessment of disease state were correlated for all patients. All the Stage III or IV patients clinically considered in complete or partial response underwent a second-look laparotomy at the end of 5 or 6 cycles of chemotherapy. Currently, a correlation has been established in 30 patients between antigen levels and the pathological response found on second-look. CA 125 assay. The immunoradiometric assay utilizes the purified OC 125 monoclonal antibody on a solid-phase immunoadsorbent to bind the CA 125 in 100 t~l of serum. The bound antigen can be detected by simultaneous incubation with 125I-labeled OC 125, as described [6,8]. CA 125 amounts are expressed in arbitrary units, based on comparison with standard controls. Clinical studies described in the literature [4,5], confirmed by our curves, consider values under 35 U/ml as normal; only 1% of healthy donors have higher levels. We therefore considered as positive only antigen levels higher than this threshold. Statistical analysis. To evaluate the association between stage, histotype, grade, and the presence of the marker we used a multiple logistic model. This measures the association of each of the above independent variables with the dependent variable (presence/absence of the marker), accounting simultaneously for their interrelations.
63
CA 125 IN OVARIAN CARCINOMA TABLE 2 CORRELATION BETWEEN STAGE, HISTOTYPE, GRADE, AND C A 125 LEVELS C A 125 Levels Pos. (%)
Neg. (%)
RR (CI)"
Total (79)
1.0b 0.64 (0.06 - 6.73) 3.42 (0.89 - 13.06) 1.65 (0.11 - 24.47)
17 5 53 4
Stage I II III IV
Histotype Serous Endometrioid Clear Cell Mixed Undiff. Mucinous Grade 1 2 3
9 4 47 3
(52.9) (80) (88.7) (75)
8 1 6 1
(47.4) (20) (11.3) (25)
30 (81.1) 10 (76.9) 9 (81.8) 11 (100) 2 (66.7) 1 (25)
7 (18.9) 3 (23.1) 2 (18.2) -1 (33.3) 3 (75)
0.15 (0.01 -
1.95)
37 13 11 11 3 4
6 (42.8) 27 (93.1) 30 (83.3)
8 (57.1) 2 (6.9) 6 (16.7)
1.0 b 9.71 (1.69 - 57.71) 1.52 (0.35 - 6.58)
14 29 36
1.0 b
a RR = Relative risk; CI = confidence interval.
b Reference category.
The results of analysis are expressed, for each category of variables considered, in terms of RR (relative risk), i.e., the chance of finding the marker relative to an arbitrarily defined reference category, for which the RR is, of course, one. In this study the reference categories were Stage I, Grade I, and all the nonmucinous histotypes. Each RR is associated with its confidence interval (CI) at the 0.95 level, which shows the statistical significance of the association (i.e., P < 0.05 if the value 1.0 does not fall within the confidence interval). RESULTS
CA 125 levels over 35 U/ml were found in 43/57 patients at diagnosis (75.4%) and in 21/43 patients in follow-up (48.8%). CA 125 Levels and FIGO Stage As shown in Table 2, we analyzed 79 cases with tumor masses potentially producing the marker before surgery (57) or at recurrence (22). In the 57 patients with a serum sample at diagnosis we found 53.3% (8/15) of positivity for Stage I, 75% (3/4) for Stage II, 85.3% (29/34) for Stage III, and 75% (3/4) for Stage IV. This good correlation was confirmed in patients with recurrence, 90.9% (20/22) of whom had high levels of the marker.
64
ZANABONI ET AL. TABLE 3 CORRELATION BETWEEN SURGICAL DISEASE STATE EVALUATION AND CA 125 LEVELS CA 125 Levels
Pathological response a
Neg. (%)
Pos. (%)
CR PR NC Relapse b
15 (88.2) 2 (25) ---
2 6 2 3b
(11.8) (75) (I00) (100)
Total patients (30) 17 8 2 3
CR = Complete response; PR = partial response; NC = no change. b Patients in clinical complete response submitted to third-look laparotomy because of a stable elevation of serum CA 125.
A large number of the 79 patients analyzed had a histological diagnosis of ovarian serous cystoadenocarcinoma (46.8%). Marker levels were positive in 81.1% of these cases. Table 2 shows the relationship between histotype and antigen values. Our results are similar to those collected by others [5] and confirm the difference in the expression of the marker between the mucinous type and the others.
CA 125 Levels and Histological Grade Table 2 shows the results of analysis of the FIGO tumor grading. The percentage of positivity was larger in cases with less-differentiated tumors. Multiple logistic analysis of the three variables, stage, histotype, and grade, indicated that only Grade 2 seemed to be associated with the presence of the marker at a statistically significant level (P < 0.05). This is probably because some categories were poorly represented in this case list.
CA 125 Levels and Pathological Response At the end of five or six courses of chemotherapy, our protocols for advanced ovarian epithelial tumors include an objective intraoperative assessment of the response. Eligible for this second-look laparotomy are all patients considered in clinical complete response (CR = absence of disease) and those in clinical partial response (PR = reduction >50%). In January 1986, 30 patients with previously positive multiple samples of the tumor marker underwent this procedure. Table 3 shows the antigen levels and the pathological response, which were in agreement in 86.7% (26/30) of the cases. A negative value was associated with CR in 88.2% of the cases (15/17). In the PRs the surgical finding was related to the marker value in 75% (6/8); the two patients with negative levels had a microscopic residual tumor (patient 1) and only a vaginal nodule (patient 2). The marker was stable or increased in all five cases of stable disease (NC = no change) or relapse. We included here three patients who, being in follow-up after a CR, were undergoing third-look laparotomy because of a rise in the serum
65
CA 125 IN OVARIAN CARCINOMA TABLE 4 CLINICAL COURSE OF SIX PATIENTS WITH CA 125 ELEVATIONDURING FOLLOW-UP
Patient No.
Relapse
Time to relapse (months)
1 2 3 4 5 6
Aortic nodes Lung + liver Bowel Pelvis Vagina Pelvic peritoneum
14 5 12 1 1.5 3.5
antigen. They showed relapses in sites not reached clinically (Table 4, patients 1, 3, and 6). DISCUSSION During the last 2 decades one of the pathologist's major aims has been to discover a marker of ovarian epithelial tumors to improve treatment of this complex disease. The antigenic determinant CA 125, found by Bast, offered new prospects, especially in the long-term control of these cancers [4-8]. As reported in the literature, we found 75.4% cases positive (>35 U/ml) at diagnosis. This was in excellent correlation with the tumor burden at the time of sampling. In the advanced forms (Stages II1 and IV) the marker was present in 84.2% (32/38), compared with 57.9% (11/19) of the early cases (Stages I and 1I). Of the 43 patients for whom baseline value at diagnosis was not available, obviously fewer had positive levels (23/43). Among these patients in follow-up, 91% (20/22) of the recurrences had high marker. Until now, only 6 of these cases presented a rise in serum CA 125 before clinical relapse. Conceivably, therefore, CA 125 is produced slowly by tumors sensitive to antineoplastic drugs; in recurrences there could be a selection of cell clones with different metabolic activity, resulting in lower expression of the antigen. Considering the CA 125 levels in relation to histotype and grading, our findings are similar to those published so far: The mucinous type seems to differ from the others, producing less antigen. Unfortunately, despite the undeniable trend, the number of cases of this category was too small to reach statistical significance. An interesting finding was the correlation between the grade of differentiation of a tumor and its inversely proportional capacity to express positive serum levels of the marker. Statistical analysis found a close association with the presence of CA 125 only for Grade 2. The use of the marker in following the response during treatment was also interesting, as mentioned by Bast et al. [9]. The present study found a good correlation between the clinical outcome and CA 125 levels. A drop in antigen level was almost always associated with clinical remission, whereas a plateau or a rise accompanied a therapeutic failure. Of the 27 patients submitted to second-look laparotomy after five or six courses
66
ZANABONI ET AL.
of chemotherapy for advanced cancer, 25 were found to be in CR or PR. There were only two false negatives among the eight PRs. These very promising findings suggest it is still too soon to give up an invasive technique like second-look laparotomy. In fact CA 125 was not detectable when the tumor burden was microscopic, as in 1 of these 2 cases. This limit could be improved in the future with a more purified antibody and better sensitivity of the system. The presence of false positives in the CR series is very important, as a high marker level is a further incitement for the surgeon to take multiple random biopsies during an apparently negative second-look. We know, in fact, that there will be a recurrence in 25-30% of patients with a negative second-look. Only the long-term follow-up of these two patients in CR with positive CA 125 will tell us whether they were cases of false-positive marker or false-negative pathological response. Finally, it is interesting to note the predictive value of this assay in the followup of patients in CR (Stages III and IV) and in the early stages. In our series, high CA 125 levels preceded a clinical recurrence in six cases (Table 4). Instructive was the fact that three of these patients had relapses in sites not easily detectable by the usual gynecological examination. Their tumor recurrence was found on third-look laparotomy, made in the light of persistently high marker levels. CA 125 may, therefore, sometimes be a predictor of relapse in asymptomatic patients. We suggest, however, that at least two high values should be found before suspicion is aroused, in order to avoid false positives due to metabolic problems. At our present stage of knowledge, it is not justified to start antitumoral treatment in a patient in CR only on the basis of an increase in the marker, not documented by histological diagnosis of relapse. The goal of gynecological oncologists is to support clinical follow-up with a sensitive and specific marker useful in ovarian cancer, as has proved possible for trophoblastic disease and germinal tumors. Until the present time the only possible check of disease state in ovarian epithelial cancer was surgical laparoscopy or laparotomy. Unfortunately, we are still far from applying this marker in population screening; the lack of specificity of the tumor-associated antigens known to date, including CA 125 [10], precludes their introduction in a prevention system.
ACKNOWLEDGMENTS We are grateful to Dr. G. Valsecchi and Dr. A. Decarli (Biostatistics Institute, University of Milan) for their precious statistical advice.
REFERENCES 1. Knauf, S., and Urbach, G. I. A study of ovarian cancer patients using a radioimmunoassay for human ovarian tumor-associated antigen OCA, Amer. J. Obstet. Gynecol. 138, 1222-1223 (1980). 2. Battacharya, M., and Barlow, J. J. Ovarian cystoadenocarcinoma associated antigen (OCAA), in Compendium of Assays for Immunodiagnosis of Human Cancer (R. B. Herberman, Ed~), Elsevier, New York, pp. 527-531 (1979). 3. Del Villano, B. C., Brennan, S., Brock, P., Bucher, C., Liu, V., McClure, M., Rake, B., Space, S., Westrick, B., Shoemaker, H., and Zurawski, V., Jr. Radioimmunometric assay for a monoclonal antibody-defined tumor marker, CA 19-9, Clin. Chem. 29, 549-552 (1983).
CA 125 IN OVARIAN CARCINOMA
67
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