Mutational activation of the epidermal growth factor receptor (EGFR) gene is implicated in lung cancer; clinical and cancer genome sequencing studies have identified hundreds of mutations in the protein kinase domain. EGFR mutation testing usually focuses on common mutations like the exon 19 deletion and exon 21 point mutation (L858R). However, molecular screening methods have started to extend beyond identification of classic EGFR mutations to prevent exclusion of patients with rare or complex mutations who may benefit from anti-EGFR therapy. Rare EGFR-mutated non-small-cell lung cancers are heterogeneous: exon 20 insertions lack sensitivity to tyrosine kinase inhibitors while exon 18 or complex mutations are more sensitive and require individual assessment. Until testing for uncommon EGFR mutations evolves and studies with large number of patients are performed, knowledge of this field will remain limited.
Keywords: epidermal growth factor receptor mutations; exon 18 mutations; exon 20 mutations; non-small-cell lung cancer; tyrosine-kinase inhibitors.