Margin Proximity Correlates with Local Recurrence After Mastectomy for Patients Not Receiving Adjuvant Radiotherapy

Although considerable evidence exists regarding margin status and reexcision for patients undergoing breast conservation therapy, few data address the impact of a close margin for patients undergoing mastectomy without postmastectomy radiotherapy.

This retrospective review identified 1147 patients who underwent 1206 mastectomies with negative final margins for breast cancer from 2006 to 2010. Margin distance was analyzed as a continuous variable and dichotomized variable ((≤2 vs >2 mm). Patients undergoing adjuvant radiation therapy were excluded from the study. Uni- and multivariable analyses were used to assess the association of reexcision, proximity of the final margin, adjuvant therapy, and other clinical and pathologic factors with local recurrence (LR).

In 158 mastectomies (13.1%), a reexcision was performed for a close (n = 90) or positive (n = 68) margin. All but one were identified intraoperatively using frozen section analysis. The reexcision rates for skin- and nipple-sparing mastectomy (SSM/NSM) were higher than for simple mastectomy (SM) (19.8 vs 9.3%; p < 0.001). The overall 5-year risk for an LR was 3.8%. The risk was 3.1% for a margin greater than 2 mm and 11.2% for a margin of 2 mm or smaller. In the multivariable model, proximity of the final margin measured as a continuous variable was found to be a significant risk factor for LR (p = 0.009), whereas adjuvant endocrine therapy was found to be protective (p = 0.03). Intraoperative reexcision was not significant in the multivariable model (p = 0.23).

For patients undergoing mastectomy for breast cancer, a wider final margin correlated with a reduced risk for LR. The rates for LR were similar between SSM/NSM and SM despite higher rates of intraoperative reexcision for SSM/NSM.