The effect of margin status on local recurrence following breast conservation and radiation therapy for DCIS

Abstract

597 Background: There is no consensus on what constitutes an adequate surgical margin in patients receiving breast conserving surgery (BCS) and postoperative irradiation (RT) for ductal carcinoma in situ (DCIS). Inadequate margins may result in high local recurrence, and excessively large resections may lead to poor cosmetic outcome without oncological benefit. Methods: A comprehensive search for published trials which examined outcomes after adjuvant RT following BCS for DCIS was performed using medline and cross referencing available data. Reviews of each study were conducted, and data were extracted. Fixed and random effects methods were used to combine data. Primary outcomes were in breast tumour recurrence (IBTR) related to surgical margins. Results: Analysis of 3,606 patients from randomized trials confirms that patients with negative margins are significantly less likely to recur than those with positive margins after RT (RR 0.53, 95% CI= 0.42 to 0.66, p<0.01). Combined data from randomized and non randomized trials, of 5,500 patients, demonstrates that where the margin status is close or unknown there is significant risk of IBTR compared to a negative margin (RR=1.68, 95% CI= 1.22–2.33, p<0.01). When specific margin thresholds are examined a 2 mm margin is superior to less than 2 mm (OR=0.67, 95% CI 0.51 -0.89, p<0.01), however we saw no significant difference in the rate of IBTR between a 2 mm margin and >5 mm (OR=1.49, 95% CI 0.54 to 4.9, p>0.05). Conclusions: Surgical margins negative for DCIS should be obtained following BCS for DCIS. A margin threshold of 2mm appears be as good as a larger margin when BCS for DCIS is combined with RT. No significant financial relationships to disclose.