Nivolumab in Biochemically Recurrent dMMR Prostate Cancer

MMR-deficient cancers of any histologic type appear to be very sensitive to PD-1 blockade with pembrolizumab, and similar data are also beginning to emerge for nivolumab and other immune checkpoint inhibitors. Among the MMR-deficient cancers, the best antitumor responses are often associated with high microsatellite instability (MSI-H status), higher tumor mutational burden (TMB), and higher predicted neoantigen load. Prevalence estimates of MMR deficiency across solid tumor types range from 1% to 20% depending on the type of malignancy. In prostate cancer, 1-3% of unselected cases harbor MMR deficiency and/or microsatellite instability. For men who previously received definitive treatment for prostate cancer and subsequently develop detectable prostate specific antigen (PSA) levels, the clinical state is known as biochemically recurrent prostate cancer. The current standard of care treatment for patients with biochemically recurrent prostate cancer is either surveillance or androgen deprivation therapy (ADT). ADT has not been shown to provide a survival benefit in this setting, and the decision to initiate ADT will depend on patient preference and perceived risks of the disease. A non-hormonal therapy such as nivolumab would provide an alternative to ADT in patients with biomarker selected (i.e. dMMR, MSI-H, high TMB, or CDK12-altered) biochemically recurrent prostate cancer.