There is growing evidence that those proposing to prescribe the drug tamoxifen as a preventative measure to women supposedly at high risk of breast cancer are simply trading one form of the disease for another.
A study by GM Williams and others (The Lancet, 24 April 1993) found liver cancer in 43 per cent of rats after 6 months on the drug. Although the dosage (45.2mg per kg of body weight per day) was many times higher than would be given to women (0.8mg/kg per day), the study found that lower doses were carcinogenic over longer periods. Earlier studies have shown that doses equivalent to those given to women produce tumours in 11.5 per cent of rats.