Members of Xenobiotic metabolizing enzymes (XMEs) are CYP1A1, CYP1B1, CYP2D6, CYP2E1, mEH, NAT1 etc, which demonstrate their anti-neoplastic effects by producing reactive oxygen species (ROS) whose cytotoxic effects cause tumor cell death and are likely to impact the treatment efficacy as well as survival after treatment (20, 21). The gene discussed is NAT1; the disease is neoplasm.