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As a cause of death in women, breast cancer ranks second to stomach cancer in Korea. Age-standardized mortality rates for breast cancer have been steadily increasing during the 1980s to 1990s. There have been big differences in incidence rates for breast cancer compared to those of Western countries. Epidemiological features, i.e., trends in morbidity and mortality, various shapes of age-specific incidence curves, migrants study results, and the risk factors, however, suggest that the incidence of breast cancer might be further increasing in Korea. The key epidemiological hormonal risk factors for breast cancer are all explicable in terms of the estrogen augmented by progesterone hypothesis ; older age, family history of breast cancer, early menarche, late menopause, late full－term pregnancy, and never－having had a breast－fed child. Both the establishment of a high－risk group and the estimation of lifetime risk are essential to develop a control strategy against breast cancer. Invasive ductal carcinoma was the most common histologic type of breast cancer in Korea, and the five－year survival rate was estimated as 80~83%. Recent studies on identification of susceptibility factors, i.e., inherited metabolic capacity of glutathione－s－transferase M1, T1 enzyme activities, catechol－O methyltransferase, XRCC1, a DNA repair enzyme for single－strand break, etc. that predispose individuals to breast cancer if they are exposed to particular environmental agents may possibly give further insight into both the etiology and the prevention of this malignancy.
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