Overall Survival in Patients with Endometrial Cancer Treated with Dostarlimab plus Carboplatin-Paclitaxel in the Randomized ENGOT-EN6/GOG-3031/RUBY Trial.

ABSTRACT

BACKGROUND: Part 1 of the RUBY trial (NCT03981796) evaluated dostarlimab plus carboplatin-paclitaxel compared with placebo plus carboplatin-paclitaxel in patients with primary advanced or recurrent endometrial cancer. At the first interim analysis, the trial met one of its dual-primary endpoints with statistically significant progression-free survival benefits in the mismatch repair deficient/microsatellite instability-high (dMMR/MSI-H) and overall populations. Overall survival (OS) results are reported from the second interim analysis. PATIENTS AND METHODS: RUBY is a phase 3, global, double-blind, randomized, placebo-controlled trial. Part 1 of RUBY enrolled eligible patients with primary advanced stage III or IV or first recurrent endometrial cancer who were randomly assigned (11) to receive either dostarlimab (500 mg) or placebo, plus carboplatin-paclitaxel every 3 weeks for 6 cycles followed by dostarlimab (1000 mg) or placebo every 6 weeks for up to 3 years. OS was a dual-primary endpoint. RESULTS: A total of 494 patients were randomized (245 in dostarlimab arm; 249 in placebo arm). In the overall population, with 51% maturity, RUBY met the dual-primary endpoint for OS at this second interim analysis, with a statistically significant reduction in the risk of death (HR = 0.69; 95% CI, 0.54-0.89; P = 0.0020) in patients treated with dostarlimab plus carboplatin-paclitaxel versus carboplatin-paclitaxel alone. The risk of death was lower in the dMMR/MSI-H population (HR = 0.32; 95% CI, 0.17-0.63; nominal P = 0.0002) and a trend in favor of dostarlimab was seen in the mismatch repair proficient/microsatellite stable (MMRp/MSS) population (HR = 0.79; 95% CI, 0.60-1.04; nominal P = 0.0493). The safety profile for dostarlimab plus carboplatin-paclitaxel was consistent with the first interim analysis. CONCLUSIONS: Dostarlimab in combination with carboplatin-paclitaxel demonstrated a statistically significant and clinically meaningful overall survival benefit in the overall population of patients with primary advanced or recurrent endometrial cancer while demonstrating an acceptable safety profile.