Keytruda Monotherapy Endometrial Cancer: 43% Risk Reduction
October 27, 2026
New Keytruda monotherapy endometrial cancer results from the Phase 3 KEYNOTE-C93 trial show that pembrolizumab alone reduced the risk of disease progression or death by 43% (HR=0.57; 95% CI, 0.42-0.79; p=0.0002) compared with platinum doublet chemotherapy in patients with mismatch repair deficient (dMMR) tumors.
Keytruda monotherapy endometrial cancer: PFS and safety
Median progression-free survival (PFS) was 38.2 months with Keytruda versus 8.4 months with chemotherapy, and 36-month PFS was 52.8% versus 30.0%. Overall survival (OS), the trial’s other primary endpoint, showed a favorable trend that was not statistically significant (HR=0.77; 95% CI, 0.52-1.15; p=0.1000). Follow-up for OS is ongoing.
Confirmed objective response rate was 64.1% versus 62.1%, which was not tested for statistical significance at this analysis. Grade 3 or higher treatment-related adverse events occurred in 18.1% of patients on Keytruda versus 50.7% on chemotherapy. Grade 3 or higher immune-mediated adverse events and infusion reactions were more common on Keytruda, at 7.4% versus 3.5%.
The results were presented at the ESMO Congress 2026 Presidential Symposium on 26 October and published simultaneously in The Lancet.
Why it matters
The comparator is platinum doublet chemotherapy, which the study’s overall principal investigator describes as the frontline standard. The trial therefore tests a chemotherapy-free option against that standard in dMMR patients. PFS is one of the two primary endpoints and is the one that reached statistical significance; OS has not yet done so, and follow-up continues. Against that progression gain, the higher rate of grade 3 or higher immune-mediated events on Keytruda is the difference to weigh. For earlier context, see Syenza’s earlier coverage of the PFS benefit and the cost-effectiveness of immune checkpoint inhibitors in advanced endometrial cancer.
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