[5-Fluorouracil level and pyrimidine nucleoside phosphorylase activity in cancer patients after oral administration of doxifluridine (5'-DFUR)].

For the purpose to evaluate the distribution of 5'-DFUR in the cancerous tissues and non-cancerous tissues of 64 cancer patients (21 gastric, 25 colo-rectal and 18 breast cancers), pyrimidine nucleoside phosphorylase (PyNPase) activity and 5-FU level were determined by bioassay and GC-MS method. 5-FU levels in the plasma were also measured in all patients. Four hundred mg of 5'-DFUR was orally administrated three times a day for 3 to 7 days and just 3 hours before surgical operations. PyNPase activity and 5-FU level were significantly higher in the cancerous tissues than non-cancerous ones. 5-FU levels in the plasma were significantly lower than those in both cancerous and non-cancerous tissues. In conclusion, 5'-DFUR is expected to be an useful anticancer drug because of the selective accumulation of converted 5-FU in cancerous tissues.