Baseline PD-L1 expression on immune and tumor cells, preexisting infiltrating CD8+ T cells, and tumor mutational burden (TMB) correlate with response2–11; however, the use of these pretreatment markers are hampered by the significant overlap between responders and non-responders, limited quantity and quality of the tissue, and/or lack of standardization12–14. This evidence concerns the gene CD8A and neoplasm.