Objective The aim of this study was to describe real-world use of immune checkpoint inhibitors for women with advanced or recurrent endometrial cancer.

Methods Adult women with advanced or recurrent endometrial cancer who received at least one line of systemic treatment between January 1, 2014 and November 1, 2020, then followed to May 31, 2021 in a nationwide electronic health record-derived de-identified database. Chi-Squared test or Welch’s 2-sample t-tests were used to compare patient and clinical factors associated with immune checkpoint inhibitor treatment. Time to next treatment analyses were performed based on the treatment line of the immune checkpoint inhibitor. Sankey plots depicted patient-level temporal systemic treatment.

Results During our study period, 326 women received their first immune checkpoint inhibitor treatment, increasing from 12 patients in 2016 to 148 in 2020. Factors associated with ever receiving immune checkpoint inhibitors included disease stage (p=0.002), mismatch repair (MMR)/microsatellite instability (MSI) status (p<0.001), performance status (p=0.001), and prior radiation receipt (p<0.001) and modality (p=0.003). The most common immune checkpoint inhibitor regimen was pembrolizumab (47.9%) followed by pembrolizumab and lenvatinib (34.7%). Immune checkpoint inhibitors were given as first, second, and third or greater lines of therapy in 24.5%, 41.7%, and 46.1% of evaluable patients. The median time to next treatment was significantly longer if given as an earlier line of treatment (p=0.008). There were significant differences in treatment line of immune checkpoint inhibitor by region (p=0.004), stage (p<0.001), and prior radiation receipt (p=0.014) and modality (p=0.009). Among 326 patients who received immune checkpoint inhibitors, 114 (34.9%) received subsequent treatment including chemotherapy (43.9%), additional immune checkpoint inhibitors (29.8%), and other (26.3%) with no differences in demographic or clinical characteristics based on the type of post-immune checkpoint inhibitor treatment.

Conclusion In an observational retrospective real-world database study, immune checkpoint inhibitors were used in 14.7% of patients with advanced or recurrent endometrial cancer across multiple lines of treatment, including after initial immune checkpoint inhibitor treatment.