Prediction of a high-risk group based on postoperative nadir CA-125 levels in patients with advanced epithelial ovarian cancer

OBJECTIVE We aimed to determine the ideal cut-off of nadir serum CA-125 level for prediction of progression free survival. METHODS Among 267 patients who achieved complete remission after chemotherapy, the correlation between nadir CA-125 and progression free survival were compared among the subgroups classified according to the distribution of CA-125. The diagnostic odds ratio and area under the receiver operator characteristics curve were compared at various cut-off points. RESULTS The nadir CA-125 levels did not have prognostic value under 12 U/mL (to 75 percentile). In contrast, they were significantly correlated with progression free survival only when the CA-125 level was greater than 12, which was 75 percentile (p=0.034). In predicting progression free survival <6 and 12 months, the cut-off value of 18 (90 percentile) showed superior diagnostic performance over 10 or 12 U/mL. Compared with patients who showed nadir levels between 0 and 12 U/mL (0 to 75 percentile), those with nadir >18 U/mL showed a hazard ratio of 2.85 (95% confidence interval, 1.70 to 4.76; p<0.001); patients with nadir levels between 18 and 12 U/mL showed a the hazard ratio of 1.68 (95% confidence interval, 1.11 to 2.56; p=0.015) compared with those whose nadir levels were under 12 U/mL. CONCLUSION The predictive power of the traditional cut-off of 10 U/mL to classify a risk group or to identify high risk patients was unsatisfactory. The optimal diagnostic performance was observed at the cut-off of 18 U/mL and this can be proposed to dichotomize cut-off values to predict outcomes among individual patients.