Immune checkpoint blockade with PD1 inhibitors is the standard of care for the first-line treatment of MSI-H/dMMR metastatic CRC; however, MSI-H/dMMR represents a small proportion of CRCs, and immune checkpoint inhibitor therapy is largely ineffective for metastatic microsatellite-stable (MSS)/proficient MMR (pMMR) patients (23). Here, PDCD1 is linked to colorectal carcinoma.