Retinyl acetate prophylaxis in cancer of the urinary bladder.

Virgin female C3H/He mice (275) were fed a ration that included 0.1 per cent N-4-(5-nitro-2-furyl)-2-thiazolyl formamide (FANFT) and retinyl acetate. The mice were divided into five groups with Groups 1 through 4 receiving 300, 600, 1200, and 2400 IU of retinyl acetate per kilogram of feed plus FANFT respectively. Group 5 received 300 IU per kg of feed and no FANFT as a control. After 45 weeks the bladders were removed and inspected for neoplasms. There were no tumors found in any of the mice from Group 5. It was found that retinyl acetate significantly inhibited the formation of squamous cell tumors at all levels and inhibited transitional cell carcinoma when given as 600 IU per kilogram of feed.