Concepts and limitations in the application of radiolabeled antiandrogens, estrogens, or androgens as isotopic scanning agents for the prostate.

The distribution of labeled antiandrogens, estrogens, and androgens has been studied in the rat and dog to elucidate the principles and limitations encountered when these agents are used in radioscanning the prostate. The bulk of the label is rapidly cleared in the biliary secretions and in the urine. The concentration of label in the prostate in comparison to other tissues such as the intestines limits the application of these agents in radioscanning of the prostate. The tissue distributions were confirmed by total body radioscans of rats and dogs receiving a labeled 3'-iodinated analog of the antiandrogen flutamide (Sch 13521 or 3'-trifluoromethyl-4'-nitroisobutyranilide).