Studies on the designing of chemotherapy for gastric cancer in man, based on the tumor tissue concentration of anticancer agents.

5-fluorouracil analogs investigated in this study include a combination of uracil and Ftorafur (UFT), Ethyl (+/-)-t-butoxy-5-fluoro-hexahydro-2, 4-dioxopyrimidine r-5-carboxylate (TAC-278), and 5'-deoxy-5-fluorouridine (5'-DFUR). In a total of 45 patients with gastric cancer, tumor tissue level of 5-fluorouracil (5-FU) was determined at 2, 4, 6, 8, and 12 hours following the oral administration of drug, using a resected stomach specimen as material. As a result, it was demonstrated that oral administration of 200 mg/m2 of UFT maintained above 0.05 microgram/g (minimum inhibitory concentration: MIC) of 5-FU in tumor tissues over 12 hours in 11 of 13 patients. On the contrary, 133 mg/m2 of TAC-278, and 200 mg/m2 or 300 mg/m2 of 5'-DFUR (which is activated by thymidine phosphorylase in man) did not produce an effective 5-FU concentration in tumor tissues. Serum 5-FU level was high in order of TAC-278, UFT, and 5'-DFUR. Clinical response rates obtained with UFT (200 mg/m2 twice a day), or TAC-278 (133-200 mg/m2, 3 times daily) were 27.5% (49 of 178 cases), and 8.3% (3 of 36 cases, by Koyama et al.), respectively. Fisher's direct probability test revealed that there was a significant difference (p less than 0.05) between them in the response rate. It was considered that the measurement of concentration of anticancer drugs in tumor tissues might provide us useful information for the designing of chemotherapy of gastric cancer.