What Is Cancer. Controversy

CONTROVERSY

24. Is axillary lymph node treatment for breast cancer of therapeutic value, or does it merely help select patients who should receive chemotherapy?

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Those who believe that axillary lymph node dissection confers only information about tumor behavior rather than a therapeutic benefit usually cite the National Surgical Adjuvant Breast and Bowel Program (NSABP) B-04 trial. There was no statistically significant difference in survival curves between patients whose axilla was

treated initially and patients who received delayed treatment to the axilla. In addition to other problems, however, the study lacked the power to prove the point. To have a 90% chance of detecting a 7% survival difference between the treatment groups, the National Surgical Adjuvant Breast and Bowel Program (NSABP) should have enrolled 2000 patients (not just 550) in each arm. Hence, a substantial survival advantage caused by axillary dissection might not have been recognized. The study was not designed to prove that the two approaches were equivalent, and it has been "overinterpreted." It takes a much larger trial to prove equivalence than to show a difference. Indeed, subsequent randomized trials in the management of breast cancer, as well as evaluation of patterns of care, demonstrate an independent survival advantage conferred by treatment of the axilla. This experience with breast cancer reinforces the importance of actually understanding clinical trials.