Although recent progress in drug therapy has facilitated marked advances in chemotherapy for breast cancer, little has been achieved in the development of individualized chemotherapy. Prognostic factors such as estrogen receptor (ER), progesterone receptor (PgR), and human epithelial growth factor receptor 2 (HER2) have recently been incorporated into risk classification in the guidelines as predictive factors for treatment response, indicating that the treatment decisions for breast cancer have shifted to factors predictive of treatment response. For the selection of optimum adjuvant chemotherapy, the prediction of treatment responses and judgment of benefits and risks for individual patients are necessary, in addition to the guidelines, for which the investigation of clinical study results, the utilization of computer-based treatment decision tools, and gene profiling may be important.