Prognostic value of serum CA 125 bi-exponential decrease during first line paclitaxel/platinum chemotherapy: a French multicentric study.

Background: CA 125 assays enable treatment-response monitoring in ovarian cancer.
Methods: A multicentric study of CA 125 kinetics under paclitaxel/platinum-based chemotherapy was performed in 130 stage IIc-IV patients. CA 125 half-life and nadir concentration were compared to patient outcome. Some patients (n=38, 29.2%) presented a CA 125 bi-exponential decrease and its clinical implication was studied. Survival analyses for disease-free survival (DFS) and overall survival (OS) used univariate (Kaplan-Meier) and multivariate (Cox model).
Results: During a median follow-up time of 29 months (range 5-106 months), 111 patients (85%) relapsed and 94 (72%) died from ovarian cancer. Patients were split into 4 groups according to their pattern of CA 125 decrease: non-assessable half-life because of a low pre-chemotherapy CA 125 level (n=38), half-life < or = 14 days and mono-exponential CA 125 decay (n=18), half-life < or = 14 days and bi-exponential CA 125 decay (n=21), and half-life > 14 days (n=53). In Cox models, nadir concentration, residual tumour volume and number of chemotherapy courses were found to be independent prognostic factors for DFS and OS. The group classification was found to be an independent prognostic factor only for DFS. However, when nadir was not introduced in the models, the CA 125 kinetics groups were the most important prognostic factor for OS.
Conclusion: Characteristics of CA 125 kinetics during first line paclitaxel/platinum chemotherapy have a strong and independent prognostic value. A CA 125 bi-exponential decrease is an indicator of bad prognosis.