Background: CA 125 assays enable treatment-response monitoring in ovarian cancer.
Patients and methods: A multicentric study of CA 125 kinetics under induction chemotherapy was performed in 631 patients. CA 125 half-life was calculated by mono-compartmental logarithmic regression. Nadir CA 125 concentration and time to nadir were also studied. Survival analyses for disease-free survival (DFS) and overall survival (OS) used univariate (Kaplan-Meier) and multivariate (Cox) models.
Results: For 553 stage IIC-IV patients, 459 (83.0%) relapsed and 444 (80.3%) died from cancer. Median (range) follow up time was 32 months (2-214 months). Median (range) for CA 125 kinetics were: 263 kU/l (5-52000 kU/l) before 1st course, 15.8 days (4.5-417.9 days) for CA 125 half-life, 16 kU/l (3-2610 kU/l) for nadir and 85 days (0-361 days) for time to nadir. Pre-chemotherapy CA 125, its half-life, nadir concentration and time to nadir all had a univariate prognostic value for DFS and OS (P<0.0001). In Cox models, CA 125 half-life, residual tumour (P<0.0001 for both), nadir concentration (P=0.0002) and stage (P=0.0118) were the most powerful prognostic factors for DFS. For OS, the significant variables were similar, with age ranking last (P=0.0319).
Conclusion: Among well-established prognostic factors in ovarian cancers, CA 125 half-life and nadir concentration bear a strong and independent prognostic value.