Following dramatic initial tumor shrinkage,tumor regrowth is most frequently associated with the emergence of a secondary geneticchange, the T790M ‘gatekeeper’ mutation within the EGFR kinase domain,which restores ATP binding in the presence of drug (Pao et al., 2004; Kobayashi et al.,2005; Yun et al., 2007). Here, EGFR is linked to neoplasm.