In CRC, patients with deficient mismatch repair, MSI-H tumours showing high TMB and treated with the programmed cell death protein 1 (PD-1) inhibitor pembrolizumab as first-line monotherapy showed significantly improved progression-free survival compared to standard of care chemotherapy with or without bevacizumab or cetuximab [48]. This evidence concerns the gene PDCD1 and colorectal carcinoma.