EGFR and non-small cell lung carcinoma: For example, in EGFR-mutated non-small cell lung cancer (NSCLC), only individuals with activating mutations in exons 19 and 21 (L858R) are sensitive to the first-generation EGFR inhibitors gefitinib, erlotinib, and afatinib while those with exon 20 T790M mutations or in-frame insertions and/or duplications (codons 767 to 774) are resistant to these agents [13, 14, 15].