Epidemiology and prevention of breast cancer

Cancer of the breast affects about one in ten women in developed countries, and has an average 5-year survival rate approaching 70%. There is a great deal of scientific evidence for a number of factors that influence breast cancer risk, including female gender, Caucasian ethnic group, increased age, tallness, post-menopausal obesity, high mammography density, earlier age at menarche, later age at menopause, nulliparity, increased age at first pregnancy, lower parity overall, family history of breast cancer in first degree relatives and, finally, the presence of specific genes. A proposed etiologic model, consisting of three basic principles, is compatible with the patterns of the occurrence of the disease and with the adverse effects of most established breast cancer risk factors. According to this etiologic model, increased levels of circulating estrogens and IGF system hormones (mammotropic hormones) during the perinatal period promote the multiplication of the mammary gland specific stem cells, and the number of these cells, which is related to mammary gland mass, represents a definitive factor for breast cancer risk. As far as preventive measures and public health strategies are concerned, although a number of factors are now well established as risk determinants, this knowledge does not readily translate into effective prevention. Mammographic examination, avoidance of excess weight after menopause, physical activity and avoidance of excess consumption of alcoholic beverages constitute appropriate preventive measures.