This conclusion generated great controversy regarding the following points: (1) whether the tumors with EGFR 19 del and L858R mutations are indeed two different diseases; (2) whether first-generation EGFR-TKIs can achieve the same results as afatinib in patients who possess the EGFR 19 del or L858R mutations; and (3) whether the genetic heterogeneity of the NSCLC patients with the two genotypes is associated with different clinical responses to EGFR-TKIs. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.