Abstract

Breast cancer incidence varies considerably between Western and non-Western countries. Breast cancer incidence and mortality rates are highest in North America and Northern Europe, intermediate in Southern Europe and Latin America, and lowest in Asia and Africa. In recent years, however, a dramatic increase in breast cancer incidence has been reported in several Asian countries, including Korea. Immigrant studies have suggested that environmental rather than genetic factors are primarily responsible for the international variability and secular trend of breast cancer rates. This chapter presents current findings on environmental risk factors for breast cancer, specifically in terms of gene–environment interactions. The scope of environmental factors encompasses obesity, hormonal factors, including menstrual and reproductive history, and dietary factors, including alcohol, folate, fruits, vegetables, antioxidant vitamins, and meats and their metabolic mutagens. For each environmental factor, we reviewed articles that assessed genetic polymorphisms that have a plausible biological mechanism for breast cancer risk modification.