Utilization of immunotherapy among eligible patients with endometrial cancer (400)

Abstract

<b>Objectives:</b> The checkpoint inhibitor pembrolizumab was approved for previously treated unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) endometrial cancer on May 23, 2017, and, in combination with len- vatinib, for previously treated recurrent or metastatic microsatellite stable (MSS) endometrial cancer on September 17, 2019 (accelerated approval). The use of pembrolizumab in clinical practice after approval has not been extensively studied. The purpose of this study was to determine the frequency of pembrolizumab use among eligible patients with endometrial cancer. <b>Methods:</b> In this retrospective study, we identified patients undergoing treatment for endometrial cancer at our institution between May 2012 and June 2021. Eligibility for pembrolizumab was determined based on FDA guidelines. Patients were recorded as having received or not received pembrolizumab only if they were eligible after the respective approval dates of pembrolizumab in MSI-H/dMMR tumors or pembrolizumab/lenvatanib in MSS tumors. Descriptive statistics were used to summarize the frequency of pembrolizumab use in eligible patients. <b>Results:</b> Of 1,541 patients who had their endometrial cancer screened, 634 had documented MSS status, and 179 had documented MSI-H/dMMR status. Of the 634 MSS endometrial cancer patients screened, 42 met FDA criteria for the use of pembrolizumab; 26 (61.9%) received pembrolizumab and lenvatinib, and 16 (38.1%) did not. In the patients with MSS endometrial cancer who did not receive pembrolizumab and lenvatinib, 12 were treated with chemotherapy, three were enrolled in clinical trials, and one was lost to follow-up. Of the 179 MSI-H/dMMR endometrial cancer patients screened, 16 met FDA criteria for the use of pembrolizumab; 13 (81.2%) received pembrolizumab, and 3 (18.8%) did not (see Figure 1). All three patients with MSI endometrial cancer who did not receive pembrolizumab were treated with chemotherapy. <b>Conclusions:</b> Immunotherapy is underutilized in patients with advanced endometrial cancer, where the clear, proven benefit has been noted. There is an opportunity to improve the identification of eligible patients and increase the use of checkpoint inhibitors in endometrial cancer with continued education.