5-fluorouracil with cytosine arabinoside in metastatic gastrointestinal cancer.

A 2-drug combination chemotherapy regimen of 5-fluorouracil (FU) and cytosine arabinoside (ara-C) was used in 23 patients with gastrointestinal cancer. The drugs were administered as a mixture by daily continuous infusion for 5 days at 4-wk intervals. Dosages for each drug were: FU, 1.1 gm/m2/day and ara-C, 50 mg/m2/day. The incidence of leukopenia (WBC, less than 3,500/mm3) was 36% and of thrombocytopenia (platelets, less than 125,000/mm3), 18% during 33 courses administered at full doses. No clinical antitumor effects were observed in 18 patients evaluable for therapeutic response. The addition of ara-C to a nonmyelosuppressive dose schedule of FU results in potentiated marrow suppression, and the antitumor effect for the combination is less than would have been predicted for either drug alone.