Progression-free survival (PFS) in primary advanced or recurrent endometrial cancer (pA/rEC) in the overall and mismatch repair proficient (MMR/MSS) populations and in histological and molecular subgroups: Results from part 2 of the RUBY trial

Abstract

Background: In Part 1 of the phase 3 RUBY trial (NCT03981796) in pA/rEC, patients (pts) receiving dostarlimab (dostar)/carboplatin-paclitaxel (CP) exhibited significant benets in PFS and overall survival versus CP alone. Outcomes may be further improved by adding a poly(ADP-ribose) polymerase inhibitor (PARPi). Here we report results from Part 2 of RUBY of dostar/CP followed by dostar/niraparib (nira; a PARPi) maintenance therapy in pts with pA/rEC. Methods: Pts were randomized 2:1 to dostar 500 mg IV + CP Q3W for 6 cycles followed by dostar 1000 mg IV Q6W + nira (individualized starting dose of 200 or 300 mg) PO daily for 3 years from randomization or to placebo (PBO) + CP Q3W for 6 cycles followed by PBOs for 3 years. The primary endpoint was PFS in the overall and MMRp/MSS populations. Results: 291 pts were randomized (192 dostar/CP + dostar/nira; 99 PBO/CP). PFS was significantly improved in pts receiving dostar/CP + dostar/nira vs PBO/CP in the overall and MMRp/MSS populations (Table). In pts with endometrioid carcinoma, pts with other histologies, and across most biomarker subgroups (eg, TP53mut), the hazard ratio (HR) directionally favored dostar/CP + dostar/nira in the overall and MMRp/MSS populations. The safety pro fi le observed was consistent with those of the individual agents.