Pembrolizumab monotherapy is associated with longer time to next treatment than chemotherapy in a real-world dMMR endometrial cancer study

Pembrolizumab is an anti–PD-1 monoclonal antibody tested here as first-line (1L) chemotherapy-free monotherapy in a US Flatiron real-world retrospective cohort of dMMR/MSI-H advanced or recurrent endometrial cancer (n=228; pembrolizumab n=80; carboplatin-paclitaxel n=148; index ≥May 1, 2017; database January 1, 2013–June 30, 2025). Median real-world time on treatment (rwTOT) was 9.1 months (95% CI 5.1–14.5) with pembrolizumab vs 3.5 months (95% CI 3.4–3.5) with carbo/pac, and median real-world time to next treatment or death (rwTTNT) was 16.6 months (95% CI 9.4–32.3) vs 5.8 months (95% CI 5.4–6.2), respectively; among patients with prior neoadjuvant/adjuvant platinum (n=41), rwTOT/rwTTNT were 12.2/23.1 months for pembrolizumab vs 3.1/5.4 months for carbo/pac. While carboplatin-paclitaxel has historically been the first-line backbone, current treatment commonly combines chemotherapy with immunotherapy followed by maintenance. Pembrolizumab monotherapy may offer a chemotherapy-free alternative for selected patients with dMMR/MSI-H disease. In July 2026, Merck announced that the randomized Phase 3 KEYNOTE-C93 trial met its progression-free survival endpoint, favoring pembrolizumab alone over platinum-doublet chemotherapy. Overall survival data remain immature, and detailed efficacy and safety results are expected at ESMO later this month.