Treatment patterns and real-world clinical outcomes in patients with advanced endometrial cancer who are microsatellite instability (MSI)-high or are mismatch repair deficient (dMMR) in the United States.

ABSTRACT

OBJECTIVES: Microsatellite instability-high (MSI-H) and deficient DNA mismatch repair (dMMR) status have emerged as actionable biomarkers for advanced endometrial cancer (aEC). The objective of this study was to assess clinical outcomes and treatment patterns among MSI-H/dMMR aEC patients who had disease progression following prior systemic therapy (FPST) in the US. METHODS: Endometrial Cancer Health Outcomes (ECHO) was a retrospective, medical chart review study of patients with MSI-H/dMMR aEC who had disease progression between 07/01/2016 and 12/31/2018 FPST and were not candidates for curative surgery. Data on patient demographics, clinical and treatment characteristics, and clinical outcomes were collected. Kaplan-Meier analyses were performed to estimate real-world progression-free survival (rwPFS) and overall survival (OS), stratified by drug class. RESULTS: A total of 124 eligible patients who initiated second-line chemotherapy ± bevacizumab or immunotherapy were included. Mean age was 61.4 years at aEC diagnosis and 86.3% of patients were stage IIIB-IV. Median rwPFS and OS were 4.0 months (95% CI 2.0-9.0) and 7.0 months (95% CI 5.0-18.0), respectively, among 21 patients who received chemotherapy ± bevacizumab, and 29.0 months (95% CI 18.0-NE) and not reached (95% CI 30.0-NA), respectively, among 103 patients who received immunotherapy. Most patients (n = 92) received pembrolizumab; among these patients, rwPFS and OS were 29.0 months (95% CI 18.0-NE) and 30 months (95% CI 30.0-NA), respectively. CONCLUSIONS: Real-world evidence suggests that pembrolizumab monotherapy provides considerable clinical benefits and has become the standard of care for MSI-H/dMMR aEC patients FPST who are not candidates for curative surgery in real-world settings.