SWOG-S9635 Fluorouracil Plus Ethynyluracil in Advanced Colorectal Cancer Not Responded to Fluorouracil

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Ethynyluracil may help fluorouracil kill more cancer cells by making tumor cells more sensitive to the drug.
PURPOSE: Phase II trial to study the effectiveness of fluorouracil plus ethynyluracil in treating patients with advanced colorectal cancer that has not responded to fluorouracil.