EGFR and lung cancer: The patterns of resistance in 1st and 2nd generation EGFR-TKIs are largely overlapping and primarily involved activation of the MAPK-PI3K pathway, cell cycle gene alterations, rearrangements of RET or ALK kinases, and many other genomic alterations, which lead to primary and acquired resistance against EGFR-TKIs in lung cancer (Figure 1) (12).