A theoretical superiority of 5-fluorouracil (FUra) activity when combined with l-leucovorin (LV) might be postulated on the basis of a possible interference of the inactive d-stereoisomer of LV with the active l-form. We treated 47 patients by means of FUra (370 mg/m2/day) and l-LV (100 mg/m2/day), for 5 consecutive days, every 4 weeks. An objective response was observed in 12 patients (25.5%, 95% confidence interval: 12.5-38.5%), with 2 complete responses. As regards toxicity, 53.1% of the patients experienced mucositis, 51% diarrhea, 31.9% nausea and vomiting, 12.7% leukocytopenia, 8.5% cutaneous toxicity, 4.25% neurotoxicity, conjunctivitis and phlebitis. This regimen appears to be substantially superimposible to the classic FUra/d,l-LV combination. Therefore, the use of l-LV, in those countries where this compound is commercially available, should not be discouraged.

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