PDCD1 and metastatic melanoma: Historically, median survival estimates were between 5.5 and 9 months.1, 2, 3, 4 In the past decade, however, a myriad of novel immunotherapies [anti-programmed cell death protein 1 (anti-PD-1) and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA4) antibodies] and targeted drugs [B-type Raf proto-oncogene (BRAF) and mitogen-activated protein kinase (MEK) inhibitors] became available for metastatic melanoma.5