Figure 1.

Exogenous exposures and endogenous DNA repair defects lead to an accumulation of mutations that may give rise to tumors in the lung. Tumor mutations can be detected and quantified in both blood and tumor tissue through NGS techniques. A subset of DNA variants represents germline polymorphisms or technical artifacts, which can be subtracted through the use of paired-tumor normal sequencing or bioinformatic approaches. The number of mutations detected is represented as tumor mutation burden—one of the many variables that may influence response to immune checkpoint blockade. ctDNA, circulating tumor DNA; GEP, gene expression profiling; NGS, next-generation sequencing; PD-L1, programmed death-ligand 1; PD-L2, programmed death-ligand 2; TMB, tumor mutation burden; WES, whole-exome sequencing.