EGFR and non-small cell lung carcinoma: The detection frequency of pre-existing EGFRT790M is highly variable, depending on the detection method (2–80%) (Wang et al. 2016) and is associated with decreased progression free survival and overall survival (Lee et al. 2014), suggesting that pre-existing EGFRT790M is an intrinsic resistance mechanism to EGFR inhibition in EGFR mutant NSCLC.