CD8A and lung cancer: TMB, DNA mismatch repair deficiency, gut microbiome, the intensity of CD8+ cell infiltration, PDL1 are potential biomarkers, increased response of ICIs in increased TMB, lung cancer has increased TMB, abnormal gut microbiome due to use of antibiotics before ICIs decrease the effect, no enhanced effect of ICIs in EGFR + group, pembrolizumab increase OS and PFS in EGFR–/ALK– lung cancer