Since PD-L1 cannot act as a comprehensive and independent biomarker in clinical practice, several efforts have been made to identify additional biomarkers potentially able to effectively predict the treatment response to ICIs, such as the abundance of CD8+ TIL infiltration, tumor mutational burden (TMB), mismatch repair deficiency (dMMR), microsatellite instability (MSI) and PD-1 copy number alteration (CNA). This evidence concerns the gene CD8A and neoplasm.