Beyond EGFR TKI in EGFR-mutant non-small cell lung cancer patients: main challenges still to be overcome.

First line epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) is the standard treatment in advanced EGFR-mutant Non Small Cell Lung Cancer (NSCLC) patients, with an improvement in response rate, progression free survival, and quality of life compared with upfront chemotherapy. However, in the real world, EGFR mutation results often return positive once chemotherapy has been started. Different clinical strategies have been tested in this situation: reserve the EGFR TKI until tumor become resistant beyond chemotherapy, stop chemotherapy and switch to EGFR TKI, introduce the EGFR TKI as a maintenance treatment, or combined strategies such as intercalated or concurrent EGFR TKI plus chemotherapy. In this review, we aim to summarize the clinical evidence of first line treatment strategy with EGFR TKI and discuss the potential options in the sequence of treatment in EGFR-mutant patients.