Background: Previous findings from a clinical trial (Protocol B-06) conducted by the National Surgical Adjuvant Breast and Bowel Project (NSABP) indicated the worth of lumpectomy and breast irradiation for treating breast cancer. After the discovery by NSABP staff members of falsified information on patients enrolled in the study by St. Luc Hospital in Montreal, separate audits were conducted at St. Luc Hospital and other participating institutions. We report the results of both audits and update the study findings through an average of 12 years of follow-up.
Methods: Patients with either negative or positive axillary nodes and tumors 4 cm or less in diameter were randomly assigned to one of three treatments: total mastectomy, lumpectomy followed by breast irradiation, or lumpectomy without irradiation. Three cohorts of patients were analyzed. The first cohort included all 2105 randomized patients, who were analyzed according to the intention-to-treat principle. The second cohort consisted of 1851 eligible patients in the first cohort with known nodal status who agreed to be followed and who accepted their assigned therapy (among those excluded were 6 patients from St. Luc Hospital who were declared ineligible because of falsified biopsy dates). The third cohort consisted of the patients in the second cohort minus the 322 eligible patients from St. Luc Hospital (total, 1529 patients).
Results: Regardless of the cohort, no significant differences were found in overall survival, disease-free survival, or survival free of disease at distant sites between the patients who underwent total mastectomy and those treated by lumpectomy alone or by lumpectomy plus breast irradiation. After 12 years of follow-up, the cumulative incidence of a recurrence of tumor in the ipsilateral breast was 35 percent in the group treated with lumpectomy alone and 10 percent in the group treated with lumpectomy and breast irradiation (P < 0.001).
Conclusions: Our findings continue to indicate that lumpectomy followed by breast irradiation is appropriate therapy for women with either negative or positive axillary nodes and breast tumors 4 cm or less in diameter.