Endometrial cancer (EC) is an increasingly common malignancy affecting the inner lining of the uterus. Advanced and recurrent EC is associated with a poor prognosis, therefore, therapies such as immunotherapies (IO) have been developed to treat these ECs. Two of these IO are pembrolizumab, and dostarlimab.

An audit was undertaken at The Christie Hospital, evaluating the patient records of 55 EC patients, undergoing IO as treatment for their advanced or recurrent EC between 1st January 2023, and 13th April 2025. Two principal treatment groups where those prescribed pembrolizumab and lenvatinib (P&L), and those prescribed dostarlimab monotherapy (DM). Efficacy, safety and tolerability of these treatments were evaluated and compared.

Most patients in this study received P&L (36 vs. 17 receiving DM). One patient received pembrolizumab monotherapy, and one received dostarlimab, carboplatin and paclitaxel. Rates of discontinuation were higher in the P&L group (72.2% vs. 58.8%). The most common reason for discontinuation was disease progression. For 9 (34.6%) P&L patients treatment related adverse effects (TRAE) led to treatment discontinuation. No DM patients discontinued treatment due to TRAE alone. Progression free survival (PFS) in the DM group was longer than in the P&L group (11.05 vs. 6.59 months (CI 95%, p = 0.035)). Overall survival (OS) in the DM group was also longer than in the P&L group (14.89 vs. 12.69 months). This difference in means was not statistically significant. This may be due to increased rates of MMR deficiency in the DM group, as this study also found dMMR ECs were associated with improved PFS, although OS was similar. 96.4% of patients experienced TRAE. Rates of hospitalisation and discontinuation due to TRAE were higher in the P&L group (50% vs 29.4% and 30.6% vs 5.88% respectively). Rates of severe TRAE were higher in the P&L group compared with the DM group (50% vs 23.5%). One DM patient died due to TRAE.

DM was found to be more tolerable, associated with fewer TRAE and less hospital admissions than P&L. DM was also associated with improved PFS and OS although this may be due to the MMR deficiency in the DM group. Given these findings, further studies into the efficacy of DM for patients with pMMR ECs may be beneficial. One patient died due to adverse effects associated DM. No patients taking P&L died. The patient sample size for this audit is small, and so, further studies are needed to ensure the reliability of these findings.