CA-125 in ovarian cancer: relation between half-life, doubling time and survival

In a retrospective study of 35 patients with stage III-IV ovarian cancer, the probability to reach a complete (CR) or partial remission (PR) was studied by comparing the initial level, half-life and normalisation time of CA-125 during chemotherapy. In 15 CR patients, pretreatment CA-125 level was lower (70 U/l, range 16-1500 U/l) than in 20 PR patients (800 U/l, range 60-9000 U/l). The median normalisation time (NT) was 6 weeks in CR (range 0.7-5.5 months) and 4 months in PR patients (range 1.2-9 months). Marker half-life was 12 days for the CR group (range 4.5-30 days) and 21 days for the PR group (range 5.5-39 days). Remission duration (r = 0.56) and log cell kill (r = 0.72) were correlated with survival. Combining initial tumour diameter, marker level and NT predicted CR in 87.5% and PR in 86%. Estimating log cell kill by combining marker half-life and doubling time gives more insight into tumour cell kinetics and individual survival.