EGFR T790M (threonine to methionine mutation at codon 790 of EGFR) gatekeeper mutation is the most common mechanism of acquired resistance to EGFR-TKIs and it has been detected in over 50% of resistant NSCLC patients and from EGFR-TKIs resistant cell lines [16–18] (Figure 2). Here, EGFR is linked to non-small cell lung carcinoma.