Tissue biomarkers of response to anti-PD-1 immunotherapies in melanoma

Prognosis and treatment of advanced melanoma have been transformed by the success of immunotherapies, in particular agents targeting PD-1. PD-L1 expression assessed by immunohistochemistry in not an effective predictive biomarker to select patients in this tumor type, since significant clinical benefit was observed in the group of patients with negative tumors. The predictive value of PD-L1 testing to select patients for combination of anti-PD-1 and anti-CTLA-4 agents is under evaluation. Other tissue biomarkers are emerging to identify sensitive tumors to anti-PD-1 agents. In particular, assessment of immune infiltrates in tumor tissue, mutational load and tumor neoantigens seem promising in melanoma.