S-1 increases the blood 5-FU concentration by inhibiting the metabolism of 5-FU by means of dihydropyrimidine dehydrogenase (DPD) and shows significant effectiveness to adenocarcinoma with high-DPD activity of the stomach [35-37], pancreas [38,39], biliary tract [40-42], and so on [43,44]. Here, DPYD is linked to adenocarcinoma.