526 The predictive role of platinum-based chemotherapy combinations on the effectiveness of PARP-inhibitors as maintenance therapy in the platinum-sensitive recurrent ovarian cancer: an observational MITO study

Introduction/Background State of the art therapy for recurrent platinum sensitive and PARP inhibitors (PARPi) naïve ovarian cancer (OC) patients includes platinum-based chemotherapy (carboplatin single agent or combined with paclitaxel, gemcitabine or pegylated liposomal doxorubicine) followed by PARPi as maintenance. Aim of the present study is to assess the predictive role of different platinum-based CT combinations on the effectiveness of PARPi in patients with platinum sensitive recurrent OC. Methodology This retrospective observational study included relapsed OC patients that received platinum-containing regimen followed by PARPi as maintenance, at the time of first or subsequent platinum sensitive recurrence. Primary endpoints were progression free survival (PFS) and overall survival (OS). Results Among 519 patients enrolled, 16.2% (84) received carboplatin as monotherapy and 80% (415) a doublet of platinum-based CT. Specifically, 16.4% (86) patients were treated with platinum-paclitaxel, 30.6% (159) with platinum-pegylated liposomal doxorubicin (PLD) and 32.8% (170) with platinum-gemcitabine. No statistical difference was found in terms of PFS between patients treated with the platinum-monotherapy and those treated with a doublet (mPFS 13.6 vs 14.4 months), but patients who received doublet had longer OS (mOS 29.7 vs 50.8 months; HR 0.6, p=0.03). According to specific CT doublets, no statistical difference was found in terms of PFS and OS, but a trend toward an increase in PFS was reported in patients treated with platinum-PLD. Specifically, a longer PFS was found in patients treated with platinum-PLD compared to platinum-gemcitabine (mPFS 17.2 vs 13 months) (figure 1). Conclusion Regardless of the type of associated drug or whether monotherapy is used, platinum remains the drug that most correlates with the effectiveness of PARP inhibitors. However, the combination platinum-PDL seems to be the most advantageous, especially when compared to platinum-gemcitabine. Disclosures The authors have the following conflict of interests: F.S.: GSK, MSD, Astrazeneca, Roche; C.D.A.: Novartis, Daiichi Sankyo, GILEAD, GSK, Astrazeneca, Roche, Pfizer, Seagen; G.S.: Clovis, MSD, Tesaro, Johnson D.L.: Clovis, MSD, GSK, Gemnab, Astrazeneca, Immunogen, Oncainvest, Pharmamar. The other authors declare have no conflict of interest.