The prognostic significance of pre- and post-treatment CA-125 in grade 1 serous ovarian carcinoma: A Gynecologic Oncology Group study

•In this ancillary GOG study, pre-treatment CA-125 was not associated with survival in women with grade 1 serous ovarian carcinoma.•Serial CA-125 measurements during platinum/taxane-based chemotherapy were associated with disease progression and overall survival.•CA-125 is a biomarker for residual disease status and response to treatment in this patient cohort.

ObjectivesThe study objective was to determine the prognostic significance of serum CA-125 levels in patients with grade 1 serous ovarian carcinoma (SOC) enrolled in a Phase III study.MethodsAn ancillary analysis of a phase III study of women with advanced epithelial ovarian cancer treated with carboplatin/paclitaxel versus triplet or sequential doublet regimens. Grade 1 SOC was used as a surrogate for low-grade serous carcinoma.ResultsAmong 3686 enrolled patients, 184 (5%) had grade 1 disease and CA-125 levels available. For those with grade 1 SOC, the median patient age was 56.5; 87.3% had Stage III disease. Median follow-up was 102 months and there was no difference in pre-chemotherapy CA-125 by treatment arm (P = 0.91). Median pretreatment CA-125 for those with grade 1 SOC was lower (119.1) than for patients with grade 2-3 SOC (246.7; P < 0.001). In those with grade 1, pretreatment CA-125 was not prognostic of outcome. However, patients with CA-125 levels that normalized after cycle 1, 2 or 3 were 60-64% less likely to experience disease progression as compared to those who never normalized or normalized after 4 cycles (P ≤ 0.024). Normalization of CA-125 levels before the second cycle was negatively associated with death, with a HR of 0.45 (P = 0.025).ConclusionsPretreatment CA-125 level was significantly lower in women with grade 1 SOC compared to those with high-grade SOC. While pretreatment CA-125 was not associated with survival, serial CA-125 measurements during chemotherapy treatment were prognostic, with normalization before the second chemotherapy cycle associated with a decreased risk of death.