A Pathologic Assessment of Adequate Margin Status in Breast-Conserving Therapy

Background The definition of a clear margin in breast-conserving therapy is uncertain. The purpose of this study was to correlate the tumor-margin distance of the excision specimen with the presence of residual tumor at reoperation. We also analyzed predictors of compromised margins and of residual disease. Methods All patients who underwent breast-conserving therapy for invasive disease from 1999 to 2003 were reviewed. Pathologic characteristics and the precise tumor distance from the radial margin were recorded. A radial margin was compromised if invasive or (ductal) in situ carcinoma was <5 mm from the margin. Results Of the 612 patients who underwent breast conservation, 211 (34%) had compromised margins, and 39 had undetermined margins. Of the 161 patients who had a reoperation for compromised margins, 87 (54%) had residual disease. Residual disease after reoperation was present in 58% (56 of 96), 56% (9 of 16), and 45% (22 of 49) of those with tumor-margin distances <1 mm, ≥1 and <2 mm, and ≥2 and <5 mm, respectively. There was a progressive decline in residual disease for each millimeter until a rate of 22% for tumor-margin distances of ≥4 mm and <5 mm was reached. Pathologic size (P = .004), an extensive intraductal component (P = .002), referral from a symptomatic rather than a population-based screening program (P = .02), and the absence of a preoperative diagnosis by core biopsy (P < .0001) were predictive of compromised margins. Only young age (<45 years) was predictive of finding residual disease on reoperation (P = .02). Conclusions A total of 45% of patients who had tumor 2 to 5 mm from the radial margin had residual disease on reoperation. Our results support a policy of requiring a 5-mm margin in patients undergoing breast-conserving therapy for invasive disease.