Chemoprevention Trial - Anastrozole in Ductal Carcinoma In Situ (DCIS) in Postmenopausal Women

Breast cancer is one of the most common cancers seriously afflicting women in the United States. Of the one million incident cases that are reported annually there are approximately 193,000 new cases of breast cancer (Greenlee, 2001). Although significant advances have been made both in early detection and treatment of breast cancer, the impact of these on reduction in mortality has been modest (Peta, 2000). Furthermore, despite data implicating diet and other environmental risk factors, no lifestyle changes have yet been shown to significantly reduce the risk of breast cancer. Therefore, chemoprevention of breast cancer is a worthwhile approach to reduce the incidence of breast cancer. There is every reason to believe that a detailed understanding of the initiation, promotion and growth of breast cancer will ultimately provide a rational strategy upon which to base prevention strategies. While the pathways of breast cancer development are not yet fully understood, a role for estrogens in breast cancer etiology has been well established. While many pathways are involved in breast cancer etiology, including loss of tumor suppressor function by p53 or BRCA1 and gain of HER2 oncogene expression, their exact role in an individual patient's cancer development may vary. Therefore, it may be advantageous to focus on a chemoprevention strategy that may have a more uniform impact on breast cancer development, such as estrogen exposure. Estrogen and its metabolites, both in the circulation and locally synthesized in the breast, are important in the pathogenesis of breast cancer. High levels of circulating estrogen in postmenopausal women have been associated with an increased risk of breast cancer (Clemons, 2001). Furthermore, local estrogen synthesis, i.e. aromatase activity, in the breast may also be important in the development of breast cancer.