Chemotherapy of chemically-induced colorectal tumours.

Benign and malignant tumours were induced in the large bowel of rats by the carcinogen 1,2-dimethylhydrazine (DMH). Benign tumours appeared from week 20 onwards and malignant tumours from week 30. 5-Fluorouracil was administered intraperitoneally in maximally tolerated doses from week 26 onwards and failed to influence significantly the development of either benign or malignant tumours. Tumours induced by DMH are a close model of human colorectal cancer and suitable for testing anticancer drugs. Agents with greater activity against colorectal cancer are required.