Distribution of ¹⁸F-5-Fluorouracil in tumor-bearing mice and rats

Extensive distribution studies of ¹⁸F-5-fluorouracil (¹⁸F-5-FU) in control and tumor-bearing mice (seven lines) and rats (eight lines) that have been shown or suspected to be responsive; to 5-FU treatment were investigated with ¹⁸F-5-FU. Studies were performed as a function of time, loading dose of 5-FU, and after a pretreatment regimen of 5-FU. Following the parenteral administration of ¹⁸F-5-FU to tumor-bearing mice and rats there was slight preferential uptake by some of the tumor types, particularly subcutaneous leukemic tumors and breast adenocarcinomas. The degree of concentration in tumor tissue in comparison with surrounding tissues (blood, muscle) was not such as to consider the radiopharmaceutical suitable for tumor localization. However, sufficient amounts of radioactivity localized in some tu,ors so that it might be possible to determine if a correlation exists between tumor uptake and anti-tumor effect of 5-fluorouracil. Another possible area of use might be in regulating the method of administration of the chemotherapeutic agent.