A single-institute retrospective trial analyzed the efficacy of concurrent SRS and anti-PD-1 or anti-CTLA-4 therapy (defined as SRS within 4 weeks of administration of checkpoint inhibitors) in 75 patients with melanoma brain metastases and identified significantly improved median percent reduction in lesion volume with concurrent compared to nonconcurrent arms and with anti-PD-1 compared to anti-CTLA-4 arms at 3 months and 6 months [117]. This evidence concerns the gene PDCD1 and melanoma.