Purpose: To compare the efficacy and toxicity of fluorouracil (FU) and racemic leucovorin (d,l-LV) versus FU combined with the l-isomer of leucovorin (l-LV) in the treatment of advanced colorectal cancer.
Patients and methods: A total of 248 patients with advanced measurable colorectal cancer previously unexposed to chemotherapy were randomly assigned to treatment with either FU (400 mg/m2/d by intravenous [I.V.] infusion for 2 hours) and racemic LV (100 mg/m2/d by I.V. bolus injection) given for 5 consecutive days, or the combination of FU and the pure l-isomer of LV using the same dose schedule. In both treatment arms, courses were administered every 28 days if toxicity allowed for a total of 6 months, unless evidence of tumor progression was documented earlier.
Results: There were no significant differences between the FU/racemic LV and the FU/l-LV arm in the overall response rate (25% v 32%), duration of response (7.2 v 8.0 months), median time to progression or death (6.25 v 8.0 months), or median overall survival time (14.5 v 15.0 months). Except for minor myeloid toxic effects associated with FU/l-LV, there was also no significant difference in terms of adverse reactions. Gastrointestinal symptoms, specifically mucasitis and diarrhea, were less frequent and less severe in both treatment arms compared with other trials with FU/racemic LV reported in the literature, which might be because of the prolonged administration of FU used in both arms.
Conclusion: The combination of FU/l-LV produced response rates, response durations, and survival times similar to those with FU/d,l-LV. Biochemical modulation of FU by either pure l-LV or racemic LV thus appears to result in equivalent clinical efficacy.