A Case of Metastatic Castration-resistant Prostate Cancer with Tumor Mutation Burden-high Presented Remarkable Response to Atezolizumab

ABSTRACT The anti-PD-1 antibody pembrolizumab has been demonstrated to be effective for unresectable solid tumors with high-tumor mutation burden (TMB). However, the evidence for the benefit of anti-PD-L1 antibody for prostate cancer is scare. In this case report, a patient with metastatic castration-resistant prostate cancer treated with life-prolonging agents including androgen receptor signaling inhibitors and taxanes was treated with the anti-PD-L1 antibody atezolizumab for TMB-high in the BELIEVE trial (jRCTs031190104). After initiation of atezolizumab, the prostate-specific antigen level decreased and a durable partial objective response was achieved. The findings of this case support the treatment with immune checkpoint inhibitors for TMB-high prostate cancer.