This prospective single-center study examined associations between serum cytokines—TNF-α, IL-2, and IL-10—and outcomes in stage IV non-small cell lung cancer (NSCLC, n = 43) and melanoma (n = 15) patients treated with Nivolumab at the Oncology Institute in Cluj-Napoca, Romania. This evidence concerns the gene TNF and non-small cell lung carcinoma.