Tumor 5-FU-related mRNA Expression and Efficacy of Oral Fluoropyrimidines in Adjuvant Chemotherapy of Colorectal Cancer

Background: It has not been elucidated whether the clinical efficacy of oral fluoropyrimidines for adjuvant chemotherapy of colorectal cancer varies with tumor biological characteristics. Patients and Methods: A multicenter randomized trial was performed comparing oral tegafur/gimeracil/oteracil (S-1) and uracil-tegafur/ leucovorin (UFT/LV) as adjuvant therapy for stage III colorectal cancer. Postoperative survival was compared based on the 5-FU-related mRNA levels in cancer tissues. Results: Among patients with tumor expressing dihydropyrimidine dehydrogenase (DPD) mRNA within the 66.7th percentile (lower 2/3) of all cases, overall survival (OS) was significantly better in the S-1 than in the UFT/LV group. In the S-1 group, patients with low DPD-expressing tumors had significantly better OS than those with highly expressing tumors. Patients with low thymidine synthase (TS)-expressing tumors had significantly better OS than those with highly expressing tumors. Conclusion: The efficacy of oral fluoropyrimidines as adjuvant chemotherapy for colorectal cancer may be influenced by the level of 5-FU-related mRNA in cancer tissues.