Unfortunately, 30% to 40% of patients with CRC are confirmed in its advanced stage and lose the chance of surgery,[3] so chemotherapy regimen has been the optimal treatment.[4] Fluoropyrimidines (FUs), including 5-fluorouracil (5-FU) and capecitabine,[5] blocking DNA and RNA synthesis by inhibiting thymidylate synthase,[6] has widely prescribed for CRC. The gene discussed is TYMS; the disease is colorectal carcinoma.