Weekly 24-hour infusion with high-dose 5-Fluorouracil and 6s-leucovorin as a 2nd-line therapy in advanced colorectal-cancer resistant to a 5-fluorouracil/6s-leucovorin bolus combination.

Recently, experimental data suggested the possibility that resistance to 5FU may be overcome by administering the drug in a different schedule. To test this hypothesis we treated seventeen patients, who failed to respond to a common 5FU/leucovorin bolus regimen, with an intravenous infusion of 6S-leucovorin, at a dose of 250 mg/m(2), concurrently with 5FU at 2,600 mg/m(2) over a 24-hour period. Treatment was repeated every week. No patient achieved an objective response. Six patients showed stable disease and 11 progressed on therapy. The treatment with 5FU infusion, at least in this schedule, is not effective in patients with 5FU bolus resistant colon cancer.