A case of recurrent endometrial cancer with long-term complete remission following pembrolizumab-induced severe immune-related adverse event colitis.

Endometrial cancer is generally diagnosed at an early stage and has a good prognosis, although once it recurs, the prognosis is poor because of few therapeutic options. Since endometrial cancer has a high frequency of microsatellite instability-high/mismatch repair deficiency, the anti-PD-1 antibody pembrolizumab is expected to be one of the key therapeutic agents for recurrent endometrial cancer. Immune-related adverse events (irAEs) are autoimmune-like unique and occasionally life-threatening side effects of immune checkpoint inhibitors. Here, we report a rare case of recurrent endometrial cancer that showed long-term complete remission after developing relapsing severe irAE colitis following the introduction of pembrolizumab.