Background: In RUBY, a phase 3, global, randomized, double-blind, placebo (PBO)-controlled trial, dostarlimab+carboplatin/paclitaxel demonstrated significant and clinically meaningful improvement in PFS compared with PBO+CP in pts with pA/rEC. PROs are reported here. Methods: 494 pts with pA/rEC were randomized 1:1 to dostarlimab (D)+CP or PBO+CP Q3W for 6 cycles followed by D or PBO monotherapy Q6W ≤3 yrs or to disease progression. EORTC QLQ-C30 and EN24 were prespecified secondary endpoints. PROs were administered on Day 1 of each treatment (tx) cycle (C), end of tx (EOT), and at safety and survival follow-ups and reported here for C7, the end of chemotherapy (chemo) and C13, and the end of 1 yr of study. Change (chg) from baseline (BL) to C7/C13 was calculated for all scales assessed. Mixed model for repeated measures analysis was conducted to generate least-squares means (LSM), adjusting for correlations across multiple time point assessments within a pt and controlling for the BL value for the global, pain, fatigue, and physical function (PF) scores. Results: PRO outcomes were similar for D+CP and PBO+CP through the chemo period (C7). The table shows selected scores at C7 and C13 for mean (SD) and chg from BL. Further, no differences across the 3 yr period between the 2 arms were reported; LSM (standard error) for global QoL was 0.5 (1.42; P=0.72), PF was −0.7 (1.39; P=0.63), fatigue was 0.2 (1.75; P=0.91) and pain was −1.0 (1.99; P=0.62). Mean chg from BL to EOT showed improvement in back/pelvic pain for D+CP and deterioration in global QoL/GHS, social functioning, body image, and chg in taste for pts on PBO+CP. Conclusions: Dostarlimab + CP significantly improved PFS while maintaining HRQoL, further supporting its use as a standard of care in pA/rEC. Clinical trial information: NCT03981796.

*Lower scores indicate reduced symptom severity.