Moreover, treatment escalation by a newer generation of drugs is an inevitable but a rarely possible way, except for EGFR-mutated NSCLC, wherein acquired T790M mutation after administration of the first generation tyrosine kinase inhibitor (TKI) can be successfully targeted by osimertinib, the third generation TKI [141]. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.