Non-small cell lung cancer patients with ex19del or exon 21 L858R mutation: distinct mechanisms, different efficacies to treatments.

With the development of antitumor therapies, different treatment methods including monotherapy and combined therapy have achieved clinical efficacy in advanced epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC) patients. Exon 19 deletion (ex19del) and exon 21 L858R mutation are common sensitive subtypes of EGFR mutation. However, potential distinct mechanisms are found from several dimensions including molecular structures, biological behaviors, concomitant mutations, resistance mechanisms and tumor mutation burdens. More evidence indicates the prognostic difference of EGFR subgroups. This review focused on the progress of potential distinct mechanisms and outcomes in clinical trials of advanced NSCLC patients with ex19del or exon 21 L858R mutation.