CYP2C19 and cancer: Of the 30 cancer patients with genotypic EM status 11 (37%) were CYP2C19 PM ‘phenocopies’; there was no statistically significant difference between the proportions who were phenotypic PM in the two genotypic EM groups (6 out of 18 for wt/wt and 5 out of 12 for wt/var, P=0.6).