As oncology enters the immunotherapy era, programmed cell death protein 1/programmed cell death protein ligand 1 (PD-1/PD-L1) inhibitors have become first-line standard care for deficient mismatch repair/microsatellite instability-high (dMMR/MSI-H) metastatic colorectal cancer, achieving very high CR rates (75%-100%) and excellent survival outcomes (7). This evidence concerns the gene PDCD1 and metastatic colorectal cancer.