Comparison of Genome Aberrations Between Early-Onset and Late-Onset Breast Cancer

Abstract

Breast cancer is the most common cancer and the second leading cause of cancer deaths in women worldwide. Breast cancer statistics in the US shows a bimodal distribution consisting of early-onset and late-onset patients. Although the incidence of early-onset breast cancer in western population is low, the survival rate is significantly poorer before 40 years old (Yankaskas, 2005). Bonnier and his colleagues showed that the breast cancer patients under 35 years old also have poorer prognostic and possess the following characteristics: (1) a higher frequency of undifferentiated tumors, (2) histoprognostic gradeIII cancer, (3) microscopic lymph-node involvement and (4) negative hormonal receptor status (Bonnier et al., 1995). Although incidence rate of breast cancer has been decreasing in the US, this happens only in the late-onset age group (Benz, 2008). Asian women have significant lower incidence rate of breast cancer (about 25/100000 in Eastern Asia) than the western countries (about 90/100000 in Western Europe) but the rate of incidence is increasing steadily with the improvement of economics in the area. In Taiwan, the incidence of breast cancer has dramatically increased from about 13/100000 in 1980 to 49/100000 in 2005 (Chang et al., 2008). The increase in breast cancer in Asia is different from that of western countries in that the incidence of premenopausal breast cancer is proportionally higher in the Asian women. Similar trend of early-onset breast cancer is found in Africa (Kruger et al., 2007). According to clinical statistics, breast cancer patients in Taiwan are mainly identified 10 years younger than their counterparts in the western countries. Compared with the lateonset group, the early-onset breast cancer (age < or = 40) has a more aggressive clinical behavior, and its five-year survival rate for each stage is much poorer. One unique feature in