June 1st 2003
Four randomized prospective trials have evaluated tamoxifen forchemoprevention of breast cancer. The National Surgical AdjuvantBreast and Bowel Project P-1 trial reported that tamoxifen reduced therisk of invasive breast cancer by 49%. Two smaller European trials, theRoyal Marsden Hospital Chemoprevention Trial and the Italian TamoxifenPrevention Study, demonstrated no decrease in the incidence ofbreast cancer among women using tamoxifen. The International BreastCancer Intervention Study confirmed that tamoxifen can reduce therisk of breast cancer in healthy women. The Multiple Outcomes ofRaloxifene Evaluation trial, which evaluated the use of raloxifene(Evista) to prevent osteoporosis, found that the risk of invasive breastcancer decreased by 76%. A uniform theme in these trials is thattamoxifen reduces the risk of breast cancer among women at high riskfor the disease. Tamoxifen is currently approved for breast cancer riskreduction. However, because of the side effects associated with its use(ie, endometrial cancer and thromboembolism), other agents are beinginvestigated. The Study of Tamoxifen and Raloxifene is designed tocompare the efficacy of tamoxifen and raloxifene in reducing breastcancer risk. Aromatase inhibitors will also be studied in the setting ofchemoprevention for breast cancer.