Real-World Use of Dostarlimab Plus Chemotherapy in Advanced or Recurrent dMMR Endometrial Cancer: A Nationwide Cohort Study in France.

[BACKGROUND] Dostarlimab, a PD-1 inhibitor, was initially approved in Europe in 2021 for advanced or recurrent mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) endometrial cancer. The phase III RUBY trial later demonstrated improved survival with dostarlimab plus chemotherapy, leading to EU approval in this indication in 2023. However, real-world data on the use of dostarlimab in routine clinical practice remain limited.

[OBJECTIVE] This study aimed to describe patients' characteristics, survival, and safety outcomes of dostarlimab plus chemotherapy in this population.

[PATIENTS AND METHODS] We used the French National Health Data System (SNDS) to include all patients with uterine corpus cancer who received dostarlimab through the French early access program between 27 September 2023 and 30 June 2024, with follow-up until 30 November 2025. Overall survival (OS), time to treatment discontinuation (TTD), and real-world progression-free survival (rwPFS; i.e. subsequent treatment, palliative care, or death) were estimated using the Kaplan-Meier method. Safety outcomes were identified using hospitalization diagnoses and outpatient dispensing, and their prevalence was reported per 1000 person-months (PM).

[RESULTS] The cohort included 644 patients with dMMR/MSI-H endometrial cancer (median age 71 years), most with metastatic disease (73.3%). At baseline, 22.2% of patients were obese, 20.0% had cardiovascular disease, and 20.2% had diabetes. During follow-up (median [IQR]: 18.8 months [10.8-21.9]), 264 patients (41.0%) died. Median OS was not reached, and the 1-year OS probability was 72.8% (95% CI 69.5-76.3). TTD and rwPFS were lower, with median of 8.6 and 9.7 months, and 1-year survival probabilities of 35.7% (95% CI 32.2-39.6) and 44.4% (95% CI 40.7-48.4), respectively. Apart from unspecific potential immune-related adverse events (AEs; 193.6/1000 PM), hematologic AEs were the most frequent (23.8/1000 PM), mainly anemia (18.9/1000 PM), followed by digestive AEs (14.0/1000 PM).

[CONCLUSIONS] This first real-world study of dostarlimab plus chemotherapy in advanced or recurrent endometrial cancer involved an older, more comorbid, and less selected population with more advanced disease than in RUBY. Survival outcomes were less favorable, but the safety profile was comparable.