CYP3A5 is a member of the cytochrome P450 superfamily of enzymes that is involved in the metabolism of drugs, exogenous carcinogens, and endogenous molecules such as steroids.5, 6, 7, 8 Previous studies of CYP3A5 focused mainly on two aspects, namely the potential relation between CYP3A5 polymorphism and cancer risk or drug metabolism.7 This evidence concerns the gene CYP3A5 and cancer.