In various neoplasms, higher TMB seems to predict favorable outcomes related to anti-PD-1/PD-L1 immunotherapy administration; indeed, the 2021 NCCN guidelines have also allowed pembrolizumab (as a second-line therapy or beyond) for mCRPCs, showing TMB > 10 mutations/Mb [4]. This evidence concerns the gene PDCD1 and neoplasm.