Chemotherapy studies in autochthonous rat tumors: carcinomas of the forestomach.

Tumors of the forestomach were induced in male Sprague-Dawley rats by oral application of acetoxymethyl-methylnitrosamine (AMMN) in single weekly doses of 3.5 mg/kg body weight for 10 weeks. 100 +/- 5 days after the beginning of carcinogen treatment exploratory laparotomy was performed. One hundred animals in the same stage of tumor development were divided at random into one control group and four groups treated with cytostatics. Bleomycin (BLM), methotrexate (MTX), 5-fluorouracil (5FU), and 1,2-bis-(2-chloroethyl)-1-nitrosourea (BCNU) were tested in groups of 20 rats each. Only in animals receiving repeated doses of BLM a slight tumor response was observed but no increase in median survival times was seen. No therapeutic effects of the other drugs used were demonstrable.