PDCD1 and cancer: Cancer immunotherapy using immune checkpoint blockade (ICB) drugs that target programmed cell death 1 (PD1), programmed cell death 1 ligand 1 (PD‐L1), and cytotoxic T‐lymphocyte‐associated protein 4 (CTLA‐4) is a promising treatment strategy that can produce a durable response, especially for patients with metastatic cancers.