Background: Breast cancer is the most common cancer among Caucasian females. On average, 1 in 12 women will have breast cancer during their lifetime. There is a marked difference in breast cancer incidence in Chinese. In Hong Kong women, the lifetime risk is 1 in 29. BRCA1 and BRCA2 are high-penetrant cancer predisposition genes, but the prevalence and nature of mutations in these genes appear to be ethnic-specific. It is not clear if the differences in cancer incidence between Caucasians and Chinese are due to genetic or environmental factors.
Methods: In our investigation of BRCA1 mutations among Chinese female patients in Hong Kong, BRCA1 mutations were found in 3.8% (CI: 1.3-8.8%) of 130 breast cancer patients. The prevalence was higher in a separate group of 56 early onset patients, aged<45 years, (8%, CI: 2.2-19.2). Most of the mutations were different from those reported in Caucasians. A deletion 589delCT was found in three unrelated patients, which may represent a common mutation. Similar prevalence of mutations was reported in Taiwan and Singapore Chinese. Other low-penetrant cancer predisposition genes may be important in the pathogenesis of the majority of breast cancers.
Conclusions: Although the epidemiology of breast cancer is different between Caucasians and Chinese, the prevalence of mutations in the high-penetrant cancer-predisposition gene of BRCA1 is comparable. It may indicate that the role of genetic contribution to breast cancer may be similar in the two ethnic groups and the difference in epidemiology may be contributed more heavily by environmental factors.