Phase I study of 5-fluorodeoxyuridine plus cytosine arabinoside infusions in patients with solid tumors

A phase I trial was conducted in 30 patients with solid tumors, using infusions of 5-fluorodeoxyuridine (5-FUdR) plus cytosine arabinoside (ara-C). Doses of 5-FUdR administered over 2 hours daily X 5 ranged from 0.02 to 1.0 mg/kg, and these doses immediately preceded a 1-hour infusion of ara-C. These schedules were selected because 5-FUdR pretreatment had been shown to sensitize L5178Y cells in culture to acute cell death by ara-C. Dose-limiting toxicity was myelosuppression. Based upon results in this study, the recommended dose of 5-FUdR to be used in phase II trials of this combination is 0.04--0.05 mg/kg (1.6--2.0 mg/m2) given prior to ara-C at a dose of 100 mg/m2. Antitumor responses were seen in patients with head and neck cancer, breast carcinoma, and carcinoid syndrome.