Decreases in the incidence of breast cancer have not been achieved, but the
re is a downward trend in age-adjusted breast cancer mortality rates in the
United States. Recent epidemiologic investigations continue to refine our
understanding of the role of established breast cancer risk factors, such a
s reproductive characteristics and body mass index, and in the process adva
nce understanding of the etiology of breast cancer. Important strides are b
eing made in the chemoprevention of breast cancer, but clarifying the poten
tial contributions of factors such as diet, physical activity, and cigarett
e smoke to the breast cancer burden is a high priority because these lifest
yle behaviors also have important implications for primary prevention, The
role of both environmental and endogenous exposures in breast carcinogenesi
s will be more clearly elucidated by studies that account for genetic polym
orphisms, some of which may lead to differential susceptibility to harmful
agents. Curr Opin Oncol 2000, 12:515-520 (C) 2000 Lippincott Williams & Wil
kins, Inc.