These same EGFR-TKIs are also indicated in the presence of NSCLC cells expressing the EGFR exon 21 (L858R) substitution (missense) variant caused by a single nucleotide change (CTG to CGG) that encodes the substitution of an arginine (R) at codon 858 instead of the leucine (L) amino acid that is normally present and favoring drug binding. This evidence concerns the gene EGFR and non-small cell lung carcinoma.