PDCD1 and metastatic colorectal cancer: The PD-1 inhibitors—pembrolizumab and nivolumab—led to a durable response in some patients with previously treated MSI-H–dMMR metastatic colorectal cancer, a finding that contributed to Food and Drug Administration approvals of pembrolizumab and nivolumab for patients with MSI-H–dMMR metastatic colorectal cancer that has progressed after treatment, with fluoropyrimidine, oxaliplatin, and irinotecan [37,38,39,40].