5-Fluorouracil carcinogenesis in BALB/c mice.

5-Fluorouracil, a drug mainly used in the treatment of gastrointestinal tract neoplasms, was administered i.p. to BALB/c mice at the dose of 30 mg/kg body weight once a week for 50 weeks to test its carcinogenicity. The treatment induced a significant increase in lung tumor in both sexes (males, p less than 0.05; females, p less than 0.01) and tumors of the lymphoreticular system in female mice (p less than 0.001). These results suggest that 5-fluorouracil is carcinogenic in mice.