The development of prostatic adenocarcinoma in Nb rats following prolonged sex hormone administration.

The low spontaneous incidence of grossly recognizable adenocarcinomas of the dorsal lobe of the prostate in Nb rats over 13 months old (0.45%) was increased to 18.38% in 130 rats by prolonged treatment with pellets of suitable sex hormones. Although testosterone propionate alone was effective, if the testosterone propionate was combined with treatment by estrone carcinomas of the prostate occurred after a shorter interval. Tumors tended to metastasize and transplanted readily, and all were autonomous, with a single exception that exhibited the growth pattern of a typical estrogen-dependent tumor.