[Clinical effect of 5'-deoxy-5-fluorouridine (5'-DFUR)]

5'-Deoxy-5-Fluorouridine is converted to 5-Fluorouracil by pyrimidine nucleoside phosphorylase of which activity is higher in tumor tissues than in surrounding normal ones. The interim result of the phase II study of this drug showed an efficacy in breast, gastric, colorectal and head & neck cancers. Above all, some CR cases in breast cancer indicated remarkable superiority of this drug for monotherapy. The duration of response was relatively long. Even in the cases with previously negative fluorinated pyrimidine therapy, this drug showed a considerable response rate. The main side effect was diarrhea but it was controllable. Diarrhea would become a good indication for determining continuation or cessation of the treatment with this drug.