Immunotherapy and chemotherapy combinations have shown activity in endometrial cancer, with greater benefit in mismatch repair (MMR)-deficient (dMMR) than MMR-proficient (pMMR) disease. Adding a poly(ADP-ribose) polymerase inhibitor may improve outcomes, especially in pMMR disease.

This phase III, global, double-blind, placebo-controlled trial randomly assigned eligible patients with newly diagnosed advanced or recurrent endometrial cancer 1:1:1 to: carboplatin/paclitaxel plus durvalumab placebo followed by placebo maintenance (control arm); carboplatin/paclitaxel plus durvalumab followed by maintenance durvalumab plus olaparib placebo (durvalumab arm); or carboplatin/paclitaxel plus durvalumab followed by maintenance durvalumab plus olaparib (durvalumab + olaparib arm). The primary end points were progression-free survival (PFS) in the durvalumab arm versus control and the durvalumab + olaparib arm versus control.

Seven hundred eighteen patients were randomly assigned. In the intention-to-treat population, statistically significant PFS benefit was observed in the durvalumab (hazard ratio [HR], 0.71 [95% CI, 0.57 to 0.89]; = .003) and durvalumab + olaparib arms (HR, 0.55 [95% CI, 0.43 to 0.69]; < .0001) versus control. Prespecified, exploratory subgroup analyses showed PFS benefit in dMMR (HR [durvalumab control], 0.42 [95% CI, 0.22 to 0.80]; HR [durvalumab + olaparib control], 0.41 [95% CI, 0.21 to 0.75]) and pMMR subgroups (HR [durvalumab control], 0.77 [95% CI, 0.60 to 0.97]; HR [durvalumab + olaparib control] 0.57; [95% CI, 0.44 to 0.73]); and in PD-L1-positive subgroups (HR [durvalumab control], 0.63 [95% CI, 0.48 to 0.83]; HR [durvalumab + olaparib control], 0.42 [95% CI, 0.31 to 0.57]). Interim overall survival results (maturity approximately 28%) were supportive of the primary outcomes (durvalumab control: HR, 0.77 [95% CI, 0.56 to 1.07]; = .120; durvalumab + olaparib control: HR, 0.59 [95% CI, 0.42 to 0.83]; = .003). The safety profiles of the experimental arms were generally consistent with individual agents.

Carboplatin/paclitaxel plus durvalumab followed by maintenance durvalumab with or without olaparib demonstrated a statistically significant and clinically meaningful PFS benefit in patients with advanced or recurrent endometrial cancer.