Monitoring cancer antigen 125 levels in induction chemotherapy for epithelial ovarian carcinoma and predicting outcome of second-look procedure.

A retrospective analysis of 45 patients with epithelial ovarian carcinoma who underwent second-look procedure after initial cytoreduction and platinum-based combination chemotherapy was undertaken. Each patient was evaluated for the result of CA 125 after a third course of chemotherapy, the result of CA 125 prior to second-look laparotomy, and the calculated slope of regression curve for CA 125. These results were compared for a normal value of CA 125 of < 35 and < 20 IU/ml. Of the 45 patients who underwent second-look procedure, 27 had a positive outcome, while 18 were negative for residual disease. For CA 125 levels obtained after the third course of chemotherapy, a level > or = 35 IU/ml predicted a positive second-look outcome in three patients, but was not statistically significant (P = 0.143) when compared to patients with normal levels. Of patients with CA 125 > or = 35 IU/ml immediately prior to second-look procedure, nine had a positive outcome for second look, a difference that was statistically significant (P = 0.006) when compared to patients with normal levels. For the calculation of the slope of the regression curve, no statistical difference (P = 0.838) was observed between the average of the slopes of the positive-outcome group and that the negative-outcome group. The only useful prediction of second-look procedure outcome identified in this group of patients was an elevated (> or = 35 IU/ml) CA 125 immediately prior to second-look procedure. Elevated levels at this time predicted the presence of disease in 100% of patients. For the other methods of analyzing CA 125 levels during therapy, the outcome of second look could not be predicted in patients with no clinical evidence of disease. Selecting a lower normal level of 20 IU/ml did not increase our ability to predict second-look procedure outcome.