Negative margin status improves local control in conservatively managed breast cancer patients

The purpose of this study was to determine the impact of final pathologic margin status on breast relapse-free survival, distant metastasis-free survival, and overall survival in patients undergoing conservative surgery and radiation therapy for invasive breast cancer.

Between January 1970 and December 1990, 984 patients underwent conservative surgery and radiation therapy at our institution as treatment for invasive breast cancer. After lumpectomy, patients were given radiation therapy to the intact breast with or without treatment to regional nodes with the routine use of electron boost to a total median tumor bed dose of 64 Gy. Pathology reports were available for review in 871 patients. Re-excision was carried out in 294 of these patients. For this analysis, patients were divided into four groups based on final pathologic margin status: negative (n = 278), dose (typically within 2 mm, n = 47), positive (n = 55), or indeterminate (n = 491).

There were no significant differences between the groups with respect to age, histology, estrogen and progesterone receptor status, tumor location, or total radiation dose. Patients with negative margins were more likely than those with positive margins to have T1 mammographically detected lesions, to have negative nodal status, and to have undergone re-excision. Patients with positive margins were more likely to receive adjuvant chemotherapy or hormone therapy (P = 0.001). As of July 1998, with a median follow-up of 13 years, the median breast relapse-free survival, distant metastasis-free survival, and overall survival rates at 10 years for the entire cohort of patients were 86%, 81%, and 76%, respectively. Breast relapse-free survival at 10 years was 98% for patients with negative margins versus 98% for those with close margins versus 83% for those with positive margins versus 82% for those with indeterminate margins. There were no significant differences in breast relapse-free survival between patients with negative and dose margins or between patients with positive and indeterminate margins. Although the negative margin status also conferred an overall survival and distant metastasis-free survival advantage, this difference is confounded by the earlier stage of disease in these patients, and margin status did not influence overall survival in multivariate analysis.

In patients undergoing conservative management of breast cancer, negative margin status significantly improves breast relapse-free survival. Close margins appear equivalent to negative margins, and indeterminate margins appear equivalent to positive margins. Adjuvant chemotherapy or hormone therapy did not counteract the adverse impact of positive margin status. Re-excision to obtain dear surgical margins is recommended, even if a radiation boost or adjuvant systemic therapy is planned.