The contribution of recent NSABP clinical trials of primary breast cancer therapy to an understanding of tumor biology--an overview of findings.

Disagreement about local-regional management of primary breast cancer is related to differences in perception of the biology of the disease. Other factors are secondary and obscure the reality that all treatment must be related to biological considerations; otherwise, the basis for therapy is relegated to speculation and to personal experience. As a result of extensive laboratory and clinical studies during the past two decades, there has arisen an altered concept of cancer biology. The National Surgical Adjuvant Project for Breast and Bowel Cancers (NSABP) has made a major contribution to the change through findings from a series of prospective randomized clinical trials. That group of American and Canadian investigators has implemented a series of trials aimed at answering biological as well as clinical questions. Those studies have not only been concerned with defining proper local-regional treatment but have also pointed out the need for, and value of, systemic therapy when used in conjunction with operation. This report will provide an overview of past and present NSABP contributions and will consider those findings in relation to observations from other clinical trials of pertinence. It will emphasize that controversies concerning breast cancer management are related to biological issues that cannot be resolved by "populism" or appeals to emotion.