ABSTRACT
Breast cancer cells can metastasize early in tumor development, resulting in disease recurrence at distant sites even if the primary tumor and regional lymph nodes are eradicated completely by surgery and radiotherapy. Understanding breast cancer as a systemic disease dates back to laboratory and clinical studies conducted in the 1960s and 1970s (1,2). Bonadonna et al. (3) completed a landmark clinical trial in which 12 months of combination chemotherapy consisting of cyclophosphamide, methotrexate, and fl uorouracil was evaluated as adjuvant treatment for patients who had undergone radical mastectomy for primary breast cancer with positive axillary lymph nodes. Follow-up showed a signifi cant drop in rates of recurrence and increases in both disease-free survival (DFS) and overall survival (OS) rates (4).
