[Effects of 5'-deoxy-5-fluorouridine on human gastrointestinal and breast cancers xenografted to nude mice].

As a preclinical secondary screening trial, the efficacy of a new derivative of 5-fluorouracil, 5'-deoxy-5-fluorouridine (5'-DFUR), on 15 human cancers xenografted serially to nude mice of BALB/c background was evaluated in comparison with two other derivatives, tegafur and UFT. Oral administration of 123 mg/kg/day of 5'-DFUR, 25-30 times, produced effective inhibition in 5 out or 7 gastric cancers, 2 out of 3 colorectal cancers, all 3 of breast cancers and 1 out of 2 pancreatic cancers, totalling 11 out of 15 cancer lines (73%) examined. In some cases shrinkage of tumors was noted without any noticeable side effects. Although an increased dose of 185 mg/kg/day of 5'-DFUR resulted in more prominent inhibition on all 9 tumors tested, some animals suffered from severe loss of body weight or diarrhea. Comparative experiments with of equimolac doses of 5'-DFUR(123 mg/kg) and FT-207(100 mg/kg) showed that the inhibition rate of the former was higher than that of the latter in all 8 lines of cancers examined. Six experiments in particular (2 gastric, 1 colorectal, 2 breast and 1 pancreatic cancers), showed that 5'-DFUR statistically sustained more effective suppression. Direct comparisons of 5'-DFUR and UFT were also made in 5 experiments in which 3 cancers were more sensitive to the former drug. Promising results in clinical trials can be expected with the new drug 5'-DFUR for these kinds of cancers.