Smokers have a lower plasma concentration of erlotinib than do non-smokers.23, 24 Smokers also have a lower incidence of skin rash and have less clinical benefit from EGFR inhibitors compared with non-smokers.23, 24 This finding was confirmed in TOPICAL because present smokers in the erlotinib group were less likely to develop rash when compared with former smokers (odds ratio 0·29, 95% CI 0·18–0·48) or never-smokers (0·20, 0·06–0·66). The gene discussed is EGFR; the disease is Skin rash.