Significance of margins of excision on breast cancer recurrence

Randomized studies have established wide excision and radiation as an equal alternative to mastectomy in the treatment of breast cancer. The early studies mandated pathologically negative margins for those undergoing radiation. The absolute necessity of free margins is uncertain. We evaluated our experience and outcome with breast-conserving surgery and radiation in relation to margin status. Two hundred sixty patients underwent wide excision for breast-conserving therapy for breast cancer. Reexcision was performed in 149 patients. The initial margin status was correlated with the amount of residual found on reexcision and the effect on local failure. The incidence of residual disease on reexcision in patients with initial gross margin involvement, focal margin involvement, and free margins was 30%. Patients with multiple margin positivity had a 65% incidence of residual disease. Only 9% (14/149) of the reexcised patients had more than 3 mm of residual cancer. This was more likely, but not significant, in those with initial margin involvement (11/100 or 11%) than in those with free margins (3/49 or 6%, p= 0.49). The risk of subsequent local failure was 8% (12/143) in those with initial free margins and 5% (6/117) in those with initial margin involvement. Those who had any residual tumor on reexcision had a nonsignificant risk of local failure (13%) compared to those that had no residual on reexcision (4%). Positive margin on initial excision is only slightly more likely to predict for residual cancer than the finding of negative margins. Routine reexcision of patients with positive margins does not significantly increase the chance of local control in patients who receive breast irradiation.