Efficacy of olaparib maintenance therapy in patients with BRCA-mutated ovarian cancer: a retrospective analysis of real-world clinical practice data

Aim: To evaluate the efficacy of olaparib maintenance therapy in real-world clinical practice in patients with BRCA-mutated ovarian cancer. Objectives: To evaluate progression-free survival (PFS) by olaparib therapy line. To determine the predictive value of the level of the cancer marker CA-125 before therapy. To analyze the incidence of adverse events requiring dose reduction or drug discontinuation. Materials and Methods: A retrospective analysis included data of 110 patients with Stage I–IV BRCA1 / 2 mutated high-grade serous ovarian cancer, who received olaparib maintenance therapy at the St. Petersburg Municipal Clinical Oncology Dispensary from 2020 to 2024. Patients were stratified into three groups: first-line olaparib (1L, n = 64), olaparib after the first recurrence (AR1, n = 24), and olaparib after two or more recurrences (AR2+ , n = 22). Statistical analysis included Kaplan-Meier survival estimates and multivariate analysis using Cox regression. Results: The median PFS was not reached in the 1L group. In the AR1 and AR2+ groups, the median PFS was 49 and 20 months, respectively (p < 0.001). An elevated baseline CA-125 level (> 35 U / mL) before initiation of olaparib therapy was associated with a statistically significant 3.2-fold increase in the risk of progression (odds ratio [OR] 3.2; 95 % CI 1.5–6.8; p = 0.003). Toxicities requiring dose adjustment were reported in 14.1 %, 12.5 %, and 13.6 % of patients in the 1L, AR1, and AR2+ groups, respectively. Conclusions: Olaparib maintenance therapy demonstrated high clinical efficacy and a manageable safety profile in real-world settings, with the greatest benefit observed in the first-line setting. Elevated pre-treatment CA-125 levels (> 35 U / mL) are an unfavorable prognostic marker.