Effect of immune checkpoint inhibitors in gynecologic cancer associated with defective mismatch repair and a rare immunotherapy-related adverse event

Immune checkpoint inhibitors (ICIs) have improved the outcome and overall survival of patients with cancer. However, predicting the efficacy of immunotherapy remains difficult. The DNA mismatch repair (MMR) system is vital for identifying and repairing mismatched nucleotides during genetic recombination. Cancers with defective MMR involve thousands of mutations and are defined as having microsatellite instability (MSI) and demonstrate a high immunotherapy response rate. Therefore, MSI could be a biomarker for predicting the response to ICIs. Herein, we present two patients with MSI-high gynecologic malignancies who demonstrated a complete response to ICI treatment, but along with panuveitis, a rare immunotherapy-related adverse event in one of the cases.