A case of MS-Stable/TMB-High Endometrial cancer treated with pembrolizumab

Abstract

Synopsis: Pembrolizumab is an immune checkpoint inhibitor that uses anti-programmed cell death 1 antibody, and its indications have been expanding in the field of gynecology in recent years. Endometrial cancer cases that have microsatellite instability (MSI) are often high in tumor mutational burden (TMB-H), and microsatellite stable (MSS) cases are very rarely TMB-H. Herein, we report a case where pembrolizumab was highly effective against MSS and TMB-H.Key words: endometrial carcinoma, MS-Stable, TMB-High, pembrolizumab, cancer multi-gene panel testing

Pembrolizumab has a higher success rate with TMB-H compared to low TMB even in MSS cases, thus knowing the TMB status in addition to MSI is clinically important for predicting treatment efficacy.

Combination therapy with pembrolizumab and lenvatinib mesylate without companion diagnostics is covered by insurance for uterine body cancer, and opportunities to investigate MSI/TMB are expected to decrease. However, determining the MSI/TMB status through MSI testing or cancer gene panel testing is clinically useful.