The 2001 NCCN Breast Cancer Guidelines reflect the results of 5 generations of NCCN Breast Cancer Guidelines. Evidence-based guidelines, such as the NNCN Breast Cancer Guidelines, are possible only because of the availability of high-level evidence at multiple decision points in treatment. The continued performance of high quality clinical trials is central to our ability to further improve the treatment of breast cancer. The panel believes that participation in high quality clinical trials is the preferred treatment at all points in breast cancer therapy.