[摘要] Breast cancer is one of the leading causes of cancer-related morbidity worldwide [
1]. In the U.S., 235,030 new cases are expected to be diagnosed in 2014 [
2]. Of these, approximately 164,000 cases (70%) will be classified as early stage (stage I–II) breast cancer, for which the potential for cure is excellent. Although surgery is the major curative modality, adjuvant chemotherapy plays an important role in increasing cure rates for a selected group of patients. Approximately 15%�?30% of patients with stage I breast cancer and up to 40% of stage II node-negative patients will have a recurrence with local therapy alone. The disparity in outcomes within groups of similar histopathologic characteristics speaks to the incredible heterogeneity of this disease [
3,
4]. How to better define and identify these higher risk individuals has been an area of intense investigation for more than a decade [
5].
