Intermittent continuous infusion of 5-fluorouracil and low dose oral leucovorin in patients with gastrointestinal cancer: relationship between plasma concentrations and clinical parameters.

Abstract

Modulation of 5-fluorouracil (5-FU) by leucovorin and continuous infusion of 5-FU can both result in enhanced therapeutic efficacy. The main objective of this study was to determine the maximum tolerated dose (MTD) of oral leucovorin in combination with continuous infusion of 5-FU for 14 days every 4 weeks at a dose of 300 mg/m2/day in 30 patients with gastrointestinal cancer. The MTD of oral leucovorin was established at 10 mg/day. Dose-limiting toxicities were mucositis, diarrhoea and hand-foot syndrome. Plasma leucovorin concentrations were below the detection limit of the assay (< 0.5 microM). Plasma 5-FU concentrations varied considerably from 0.06 to 11.3 microM. A relation between toxicity, response and plasma concentration of 5-FU could not be established. Our data may indicate that even very low plasma concentrations of leucovorin are able to modulate 5-FU. In 17 patients with colorectal cancer the response rate was 24% (95% CI: 7-50%), which is comparable to other treatment schedules with leucovorin or to continuous infusion of 5-FU alone.