Tamoxifen and benign breast problems.

The agent tamoxifen plays an important part in the treatment of breast cancer. Although it acts as an antioestrogen by binding to oestrogen receptors, it also has oestrogen agonistic effects on the liver. Recent toxicity studies in rats have revealed that after high dosages both cataracts and hepatocellular carcinomas develop. For these reasons it has been suggested that use of tamoxifen be discontinued for the treatment of benign conditions such as severe cyclical mastalgia and also for trials on the prevention of breast cancer. It is argued that the development of hepatocellular carcinomas in rats is the result of the known oestrogen agonist activity of tamoxifen, with similar results being found in a few women receiving oral contraceptives, the use of which still continues. Studies of the use of the agent for benign conditions should evolve in the context of controlled clinical trials in order that important new indications for tamoxifen are not overlooked.