Mechanisms to TKI resistance include the development of a recurrent T790M EGFR mutation, amplification of signalling molecules that bypass EGFR inhibition (such as MET and HER2), mutations in other oncogenic drivers (eg, PIK3CA and B-RAF) and conversion to small-cell lung cancer (SCLC).64–69 In this context, the possibility to interrogate lung cancer genotype in real time through liquid biopsies is of paramount importance. The gene discussed is EGFR; the disease is lung cancer.