Platinum or non-platinum therapy in post-olaparib recurrent ovarian cancer: Analysis in matched cohorts.

5588 Background: Due to potential cross-resistance mechanisms efficacy of platinum agents may be dramatically reduced in patients with ovarian cancer which progressed during maintenance therapy with PARP-inhibitors. We conducted this study to examine whether administration of platinum compounds has clinical value in post-olaparib setting of treatment for epithelial ovarian cancer treatment. Methods: This was a single center retrospective study in matched cohorts. We selected ovarian cancer patients from N.N. Blokhin NMRCO ovarian cancer who were treated in 2014-2024 years for any FIGO stage high-grade serous or endometrioid advanced epithelial ovarian cancer and progressed during olaparib maintenance therapy. Patients were treated with standard platinum-based or non-platinum chemotherapy for recurrent advanced epithelial ovarian cancer. Cardinality matching was considered to ensure adequate balancing of the study arms. The primary endpoint of the study was progression-free survival (PFS) in patients treated with platinum-based and non-platinum chemotherapy. Overall survival was a secondary endpoint. Results: Cardinality matching with 1:2 ratio resulted in 126 matched patients for further analysis. Groups were well balanced without any significant differences in baseline characteristics. Median age in both treatment arms was 50 years with no differences in patients’ age, risk groups, prevalence of BRCA-mutations, duration of olaparib therapy and platinum-free interval. With a median follow up of 7.4 mo. median PFS was 6.0 in the non-platinum chemotherapy arm and 6.5 mo. in the platinum-based therapy arm (HR 1.17; 95% CI 0.77-1.77; p=0.46). Estimated 1-year PFS was 13.1% and 8.3%, respectively. Median OS was 21.3 mo. and 23.1 mo. in platinum-based chemotherapy arm and non-platinum arm (HR 0.98; 95% CI 0.55-1.76; p=0.96). Subgroup analyses revealed no heterogeneity in therapy efficacy. Conclusions: Our study suggest no additional benefit from platinum-based chemotherapy in post-olaparib ovarian cancer, further prospective trials are warranted to find optimal therapeutic approaches for these patients.