Capecitabine is a prodrug of 5-FU that is hydrolyzed by carboxylesterase in the liver to 5′-deoxy-5-fluorocytidine (5′-DFCR), which is then converted to 5′-deoxy-5-fluorouridine (5′-DFUR) by cytidine deaminase in the liver and tumor tissue, and 5′-DFUR is finally converted to 5-FU by thymidine phosphorylase in tumor tissue [4]. The gene discussed is TYMP; the disease is neoplasm.