Time to quality of life (QoL) improvement or deterioration in patients (pts) with primary advanced or recurrent endometrial cancer (pA/R EC) treated with dostarlimab plus chemotherapy in the ENGOT-EN6-NSGO/GOG-3031/RUBY trial.

5600 Background: In Part 1 of the phase 3 RUBY trial (NCT03981796) in pts with pA/rEC, dostarlimab + carboplatin-paclitaxel (DOST+CP) significantly improved progression-free survival and overall survival vs placebo (PBO)+CP. Patient-reported outcomes were a secondary endpoint. Here we present a post hoc analysis comparing timing of QoL improvement or deterioration by treatment. Methods: Pts were randomized 1:1 to receive DOST+CP or PBO+CP Q3W (6 cycles) followed by DOST or PBO monotherapy Q6W for ≤3 y. QoL was collected at each visit. Using data from the Sept 22, 2023 data cut (median follow-up 37.2 mo), analyses on time to first QoL improvement (TTI1) or deterioration (TTD1) were conducted for the EORTC QoL Questionnaire Core 30 (QLQ-C30) and Endometrial Cancer 24 (EN24) assessments using Cox regressions. Improvement or deterioration was classified ≥10-point change in the appropriate direction, per domain, from baseline. Results are reported for the primary study populations (overall and mismatch repair deficient/microsatellite instability-high [dMMR/MSI-H]). Results: A total of 494 pts were randomized, of which 118 were dMMR/MSI-H. For all QLQ-C30 and EN24 domains, TTI1 was similar between arms except pain in the overall population and role function in the dMMR/MSI-H population which reached nominal significance for earlier improvement in the DOST+CP arm (Table). The overall population had similar TTD1 in both arms, while time to deterioration was delayed in the DOST+CP arm for several domains (eg, global QoL, pain) in the dMMR/MSI-H population. Conclusions: With over 3 years of follow-up, DOST+CP was comparable to PBO+CP for TTI1 and TTD1 in the overall population of the RUBY trial and TTD1 was delayed in several QoL domains in the dMMR/MSI-H population. These results on patient experience of treatment further support the efficacy and safety data of dostarlimab for use in patients with pA/rEC. Clinical trial information: NCT03981796 . Overall population dMMR/MSI-H population DOST+CP (N=245)n PBO+CP(N=249)n HR, P value DOST+CP(N=53)n PBO+CP(N=65)n HR, P value Time to first improvementPainRole function 154111 13197 1.37, P =0.0081.28, P =0.076 3232 3726 1.20, P =0.4421.67, P =0.048 Time to first deteriorationGlobal QoLRole functionSocial functionPainSexual interestSexual activitySexual enjoymentUrological symptoms 194203200202126114105173 222219219218157143140201 0.85, P =0.1090.97, P =0.7960.97, P =0.7630.86, P =0.1190.82, P =0.1040.81, P =0.1020.77, P =0.0440.83, P =0.073 3336333719151330 5757575540343152 0.61, P =0.0270.58, P =0.0150.60, P =0.0200.63, P =0.0310.38, P =0.0010.42, P =0.0050.56, P =0.0920.50, P =0.003 n=number of patients with events. CP, carboplatin-paclitaxel; dMMR, mismatch repair deficient; DOST, dostarlimab; MSI-H, microsatellite instability-high; PBO, placebo.