Epidemiology, prevention, and early detection of breast cancer

Advances in the past year in understanding the etiology, early detection, and prevention of breast cancer are reviewed. Reports suggest that exogenous hormone therapy is associated with only moderate or no excess risk of breast cancer. Studies examining the association between exposure to organochlorine compounds and the risk of breast cancer are inconsistent and further investigations are required. The report by the International Workshop of Screening for Breast Cancer emphasizes the benefit in reducing breast cancer mortality to be gained by regular screening among women aged 50 years and older. Age is the strongest predictor of breast cancer risk, yet screening rates tend to diminish with age. Chemoprevention trials for the primary prevention of breast cancer are underway in North America and Europe. Agents under investigation include tamoxifen and fenretinide. The risks and benefits of tamoxifen therapy continue to be clarified with reports from a pilot prevention trial and follow-up of participants of prior adjuvant treatment trials. A beneficial effect in reducing cardiac morbidity has been observed among women taking 40 mg/d of tamoxifen for at least 2 years. Several studies demonstrated the increased risk of endometrial pathologic changes, including endometrial cancer associated with tamoxifen therapy. Because of the uncertainty of net risks and benefits, close monitoring for adverse side effects should be incorporated into ongoing prevention trials.