A single-institution retrospective exploratory analysis on the effectiveness and safety of lenvatinib plus pembrolizumab for advanced endometrial cancer: insights from ProMisE molecular classification system

Background: The Proactive Molecular Risk Classifier for Endometrial Cancer has identified four risk groups for the prognosis of endometrial cancer. Lenvatinib plus pembrolizumab was recently approved as a second-line treatment for unresectable endometrial cancer, but reports in clinical practice are lacking. The relationship between the efficacy of lenvatinib/pembrolizumab and Proactive Molecular Risk Classifier for Endometrial Cancer classification is unclear.

Methods: This single-centre retrospective study included patients who underwent lenvatinib/pembrolizumab therapy at Iwate Medical University Hospital between January 2022 and March 2023. Formalin-fixed paraffin-embedded specimens obtained from patients before treatment were collected and classified into the mismatch repair-deficient, p53 abnormal and no specific molecular profile subtypes using immunohistochemistry. The response rate, progression-free survival and adverse events were evaluated using electronic medical records. The study was approved by the hospital's ethics committee (approval number: MH2022-093).

Results: This study enrolled 20 patients, who underwent a median follow-up of 17.8 months (95% confidence interval: 16.6-18.9). The best overall response rate was 60.0% (36.1-80.9), and the median progression-free survival was 11.6 months (2.9-20.3). The median progression-free survival in the p53 abnormal group (n = 9) was 3.4 months (3.0-3.8); however, progression-free survival did not reach the median (P < 0.001) in the mismatch repair-deficient/no specific molecular profile group (n = 11). Symptomatic immune-related adverse events (except hypothyroidism) occurred in 4/20 (25.0%) patients, and partial responses were observed in all cases. No treatment-related deaths occurred.

Conclusion: The p53abn group in the Proactive Molecular Risk Classifier for Endometrial Cancer classification has a poor prognosis even after treatment with lenvatinib/pembrolizumab.