A pathologic assessment of adequate margin status in breast-conserving therapy

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. 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. 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). 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.