There was preliminary evidence of an association between BMI and CYP2C19 activity in the advanced cancer patients; according to the standard cutoff for BMI, among those with low BMI (<25) 62% (8 of 13) were PM compared with 22% (4 of 18) in patients with a high BMI (>25) (P=0.03). Here, CYP2C19 is linked to cancer.