H.-J. Senn Adjuvant Chemotherapy (ACT) of breast cancer has now emerged as one of the controversial su): >jects in clinical and also experimental oncology. Driven by growing frustration about stagnating cure rates in breast cancer [1,4] and stimulated by elegant demonstration of highly curative effects of adjuvant systemic therapy in animal models [6, 11] and in several childhood neoplasias [15], researchers introduced ACT to the primary treatment...