While adjuvant pembrolizumab is not currently FDA-approved for MCC, the anti-programmed death protein 1 (PD1) agent was chosen based on the size of this MCC lesion (despite radiation therapy), the overall immunogenicity seen in MCC, the efficacy of this therapy in systemic treatment-naïve patients, the efficacy of the therapy in stage III melanoma, and efficacy demonstrated in treating CNS metastases of melanoma [35–37]. This evidence concerns the gene PDCD1 and melanoma.