Concentration of 5-fluorouracil in renal cells from cancer patients administered a mixture of 1-(2-tetrahydrofuryl)-5-fluorouracil and uracil.

The concentrations of 5-fluorouracil (5-FU) and related compounds were studied in tissues including renal cells removed from 27 cancer patients, to whom UFT (a mixture of uracil and tegafur in a molecular ratio of 4:1) was administered orally over 5 days. The level of 5-FU in cancer tissue was two-fold that of the normal kidney (87 +/- 79 ng/g vs. 38 +/- 29 ng/g, p less than 0.005), with almost the same level of tegafur. The serum 5-FU level was as low as 4 ng/ml. These results confirm the high efficiency of UFT with minimal side-effects compared to tegafur.