Cancer patients with higher expression levels of CD8A could derive better survival outcomes when treated with anti-PD1 or anti-CTLA4, in accordance with the seminal studies of Tumeh and others (Tumeh et al., 2014), indicating that metastatic melanoma patients responding to pembrolizumab were characterized by proliferation of intra-tumoral CD8+ cells that directly correlated with a radiographic reduction in tumor size, with further multivariate analysis manifesting that CD8+ density in the invasive margin adjacent to the tumor as the best entire predictive parameter. The gene discussed is PDCD1; the disease is metastatic melanoma.