This agent was approved by the US Food and Drug Administration (FDA) in July 2013 for the first-line treatment of metastatic non–small cell lung cancer (NSCLC) in patients whose disease harbors common EGFR mutations, namely exon 19 deletions (Del19) or exon 21 (L858R) substitutions, as identified by an FDA-approved test [4]. This evidence concerns the gene EGFR and lung cancer.