67 Immunotherapy in Recurrent Endometrial Cancer: Who Derives Benefit?

Use of immunotherapy in endometrial cancer is increasing. Historically, many immunotherapy trials focused on endometrioid endometrial cancer (EEC). The objective of our study was to determine whether patients with non-EEC have derived benefit from immunotherapy-based treatments. A retrospective cohort study of patients with recurrent endometrial cancer who were treated with immunotherapy regimens prior to 2021. We defined clinically meaningful response as complete response, partial response, or stable disease lasting ≥6 months. Patients were included if they received any immunotherapy-based regimen, either as standard of care or on a clinical trial and had treatment response information available even if regimen was stopped for toxicity. Single-agent and combination therapies were included, but patients also on cytotoxic chemotherapy were excluded. Descriptive and comparative statistics were performed. 83 patients met inclusion criteria. Patient characteristics are listed in Table 1. Similar numbers of patients had EEC and non-EEC histologies and were mostly mismatch repair (MMR) proficient. When stratified by histology (Table 1), patients with EEC tumors were more likely to have MMR deficient tumors and were less likely to receive immunotherapy on a clinical trial. Most MMR deficient tumors, regardless of histology, responded to immunotherapy for ≥6 months. In the MMR proficient group, most patients were treated with immunotherapy on a clinical trial. In this subset, a similar percentage of patients with EEC and non-EEC tumors had a response that lasted ≥6 months. When looking at treatment response by race (White vs Black vs other race), there were no differences in response within the EEC (39% vs 70% vs 0%, p=0.09) and non-EEC subgroups (24% vs 31% vs 0%, p=0.79). Download : Download high-res image (320KB)Download : Download full-size image Responses to immunotherapy were seen in both the EEC and non-EEC patient subgroups. Future immunotherapy trials should include patients with non-EEC histology in their enrollment eligibility.