[Can breast cancer be prevented?].

More than six-fold variation in incidence between countries, an increasing incidence among immigrants to high incidence areas, and a general increase in the incidence of breast cancer within countries, are factors which suggest a potential for prevention. Reproductive factors such as early menarche, late age at first full term birth, nulliparity, and late age at menopause increase risk of breast cancer, but manipulation of any one of these factors does not seem to be a realistic preventive tool. Nevertheless, the future possibility of using tamoxifen as a chemopreventive agent against breast cancer is discussed, particularly in relation to women at increased risk due to familial clustering. Alcohol consumption by young women, and overweight among postmenopausal women may also increase the incidence of breast cancer. Consequently, reduced alcohol intake by young women, and weight reduction among overweight women after menopause may reduce the risk of breast cancer.