This systematic review highlights that PD-1 and PD-L1 overexpression, when used in combination with immune checkpoint inhibitor (ICI) therapy, could represent a cost-effective strategy for treating NSCLC as a first-line treatment with pembrolizumab and with both first- and second-line nivolumab, but also for renal cell and urothelial carcinoma. The gene discussed is PDCD1; the disease is non-small cell lung carcinoma.