Complete Response to Pembrolizumab in a Patient with Castration-Resistant Prostate Cancer with Both BRCA Positivity and a High Frequency of Microsatellite Instability: A Case Report.

Introduction: There have been few reports of patients for whom a cancer gene panel test for solid tumors revealed the simultaneous presence of BRCA mutation and microsatellite instability (MSI)-high status. BRCA mutations have been reported in 13% of castration-resistant prostate cancer (CRPC) patients, and 3.1% of prostate cancer cases are MSI-high/mismatch repair deficient.