However, routine use of PD-1 inhibitors in unresectable or metastatic melanoma is not guided by PD-L1 expression, and is in fact, not recommended by the NCCN Guidelines.7 Although, immune checkpoint therapy has revolutionized the field and dramatically increased survival for patients with metastatic melanoma, several randomized control trials have demonstrated that PD-L1 expression is not predictive of overall survival and progression-free survival in response to immune checkpoint inhibitors such as nivolumab in these patient populations.21, -23. This evidence concerns the gene PDCD1 and metastatic melanoma.