Response rates to second-line platinum-based therapy in ovarian cancer patients challenge the clinical definition of platinum resistance

The aim of this study was to compare response rates and survival in women with “platinum resistant” epithelial ovarian cancer (EOC) who received further platinum-based or non‑platinum chemotherapy for treatment at first relapse. Patients with high-grade EOC (including fallopian tube and peritoneal cancer) of all histologies recruited to the Australian Ovarian Cancer Study (AOCS) and treated with platinum-based primary chemotherapy were included. Response to second-line chemotherapy, overall survival (OS) and survival after treatment for first progression (OS2) were determined in all histologies and separately in women with high-grade serous tumors. Of the 341 patients classified as platinum-resistant by the 6-month threshold, 243 (71%) were treated with chemotherapy at relapse. CA-125 response rates to platinum-based chemotherapy were significantly higher compared to non‑platinum chemotherapy (51% vs 21%, P