A case-control study of breast cancer in Taiwan--a low-incidence area

Abstract

Summary To investigate risk factors for breast cancer in Taiwan, a low-incidence area, a case-control study was conducted. This comprised 244 subjects with diagnosed and pathologically confirmed breast cancer (age range 20-80 years) and 450 female ophthalmology outpatients as controls. Univariate and multiple logistic regression analysis suggests that breast cancer in Taiwan is aetiologically similar to breast cancer in high to moderate-incidence areas. A family history of breast cancer appears to be the most important factor contributing to the risk of breast cancer (odds ratio = 4.69). The effect of reproductive hormones (represented by the years of history of menses in premenopausal women, odds ratio = 3.35; or the age at menarche in post-menopausal women, odds ratio = 2.67) plays a significant role in tumorigenesis. Breast feeding appears to be a particularly important protective factor in Taiwanese women (odds ratio = 0.57).Keywords: breast cancer; cancer predisposition; reproductive hormone; breast feeding; risk factor; epidemiology Breast cancer is similar to other human cancers in that it arises from a multifactorial process. Recent attention has focused both on genetic predisposition to breast cancer (Sattin et al, 1985;Fisher et al, 1993) and on its association with factors relating to modem affluence, including diet and alcohol consumption (Hunter and Willett, 1993;Rosenberg et al, 1993). Furthermore, the effect of reproductive factors strongly supports a hormonal role in its aetiology Pike et al, 1993). Early menopause, for example, whether occurring naturally or through oophorectomy, has been shown to reduce risk significantly (Trichopoulos et al, 1973;Pike et al, 1981).While numerous studies have been conducted in Western countries to assess the epidemiology of breast cancer, there have been few studies of Asian populations. Such studies are of interest because their different risk profiles may help to explain the lower occurrence of the disease. Although breast cancer in Taiwanese women is the second most common form of cancer (Cancer Registry Annual Report in Taiwan, 1987-91) and the fourth leading cause of cancer mortality (based on Public Health Annual Report in Taiwan, 1993), compared with many Western countries Taiwan is considered to be a low-incidence area for breast cancer with an estimated age-adjusted incidence 15-20 per 100 000, which is much lower than the 60-90 per 100 000 in the UK or USA (Parkin et al, 1993 On the basis of hospital chart number, the cases were 244 women randomly selected from subjects with newly diagnosed (incident) and pathologically confirmed breast carcinoma in the age range 20-80 years. The histopathological profile included 227 cases of infiltrating ductal carcinoma and 17 cases of intraductal or intralobular carcinoma. This sample of female patients constituted about 30% of all the women with breast cancer attending our breast cancer clinic during the study period.To serve as comparable and representative controls, 450 (unmatched) women of the same age dist...

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Breast Cancer Risk Is Associated with the Genes Encoding the DNA Double-Strand Break Repair Mre11/Rad50/Nbs1 Complex

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