Treatment patterns and outcomes by mismatch repair/microsatellite instability status among patients with primary advanced or recurrent endometrial cancer in the United States

To describe real-world patient characteristics, treatment patterns, and clinical outcomes in primary advanced/recurrent endometrial cancer (pA/R EC) by mismatch repair/microsatellite instability (MMR/MSI) status who initiated first-line therapy. Data from the Flatiron Health electronic health record-derived database were analyzed from patients with a diagnosis of pA/R EC who started treatment between 1 January 2013, and 31 August 2022, from ≈ 280 US clinics. MMR/MSI status and treatment patterns were summarized; time to next treatment (TTNT) and overall survival (OS) were estimated using Kaplan-Meier methods. Of 2022 patients, 11.03%, 27.79%, and 61.18% had MMR-deficient/MSI-high (dMMR/MSI-H), MMR-proficient/microsatellite stable (MMRp/MSS), and unknown MMR/MSI status, respectively. Platinum-based chemotherapy combinations, including carboplatin-paclitaxel, were the most frequent first-line regimens (dMMR/MSI-H, 49.33%; MMRp/MSS, 55.52%; unknown, 65.08%); treatment patterns differed between subgroups. Median TTNT with platinum-based combinations were 6.87, 8.08, and 7.85 months, respectively; OS medians were 41.89, 26.18, and 21.62 months, respectively. Platinum-based chemotherapy combinations, the recommended first-line treatment, were not used in ≈ 40% of patients. TTNT rates were similar to the PFS rates in the carboplatin-paclitaxel arms in the RUBY and GY-018 trials; OS rates were similar to RUBY, highlighting the potential for combination therapies to improve outcomes.