EGFR and lung cancer: RFS has been a surrogate primary endpoint for survival in the major clinical trials to evaluate biological response to treatment, because OS reflects the effects of the treatment after progression, such as an EGFR-TKI, and the deaths from other diseases except lung cancer.13) In the subgroup analysis of JIPANG study, Takahashi et al. also showed worse RFS in the patients with lung cancer harboring EGFRmt than in those with EGFRwt lung cancer.