Patient-reported outcomes in the subpopulation of patients with mismatch repair-deficient/microsatellite instability-high primary advanced or recurrent endometrial cancer treated with dostarlimab plus chemotherapy compared with chemotherapy alone in the ENGOT-EN6-NSGO/GOG3031/RUBY trial

Objective: In the ENGOT-EN6-NSGO/GOG3031/RUBY trial, dostarlimab+carboplatin–paclitaxel demonstrated significant improvement in progression free survival and a positive trend in overall survival compared with placebo+carboplatin–paclitaxel, with manageable toxicity, in patients with primary advanced or recurrent endometrial cancer. Here we report on patient-reported outcomes in the mismatch repair-deficient/microsatellite instability-high population, a secondary endpoint in the trial. Methods: Patients were randomized 1:1 to dostarlimab+carboplatin–paclitaxel or placebo+carboplatin–paclitaxel every 3 weeks for 6 cycles followed by dostarlimab or placebo monotherapy every 6 weeks for ≤3 years or until disease progression. Patient-reported outcomes, assessed with the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 and Endometrial Cancer Module, were prespecified secondary endpoints. A mixed model for repeated measures analysis, a prespecified exploratory analysis, was conducted to generate least-squares means to compare between-treatment differences while adjusting for correlations across multiple time points within a patient and controlling for the baseline value. Results are provided with 2-sided, nominal p values. Results: Of 494 patients enrolled, 118 were mismatch repair-deficient/microsatellite instability-high. In this population, mean change from baseline to end of treatment showed visual improvements in global quality of life (QoL), emotional and social function, pain, and back/pelvis pain for dostarlimab+carboplatin–paclitaxel. Meaningful differences (least-squares mean [standard error]) favoring the dostarlimab arm were reported for change from baseline to end of treatment for QoL (14.7 [5.45]; p=0.01), role function (12.7 [5.92]); p=0.03), emotional function (14.3 [4.92]; p<0.01), social function (13.5 [5.43]; p=0.01), and fatigue (−13.3 [5.84]; p=0.03). Conclusions: Patients with mismatch repair-deficient/microsatellite instability-high primary advanced or recurrent endometrial cancer receiving dostarlimab+carboplatin–paclitaxel demonstrated improvements in several QoL domains over patients receiving placebo+carboplatin–paclitaxel. The observed improvements in progression free survival and overall survival while improving or maintaining QoL further supports dostarlimab+carboplatin–paclitaxel as a standard of care in this setting. Trial registration ClinicalTrials.gov