Earlier this week, we saw an NCDB analysis questioning the difference in recurrence risk between 2 mm DCIS margins versus narrower negative margins. Here we have another recent analysis of DCIS margins using data from NSABP-B53. B53 enrolled 3104 postmenopausal patients with hormone receptor positive DCIS and negative margins who were randomized to receive either tamoxifen or anastrozole in addition to adjuvant radiation. Margins were collected prospectively, and 1 mm was used as the threshold for close (<1) or negative (>1). This analysis further separated out those with >2 mm margins. Those with margins >1 mm had a significantly lower 10 year cumulative incidence of ipsilateral breast tumor recurrence (IBTR) than those with <1 mm margins (4% v 5.6%, P=.04). IBTR at 10 years was also lower when using the 2 mm threshold (5.3% v 3.8%, P=.05). However, in multivariable analysis accounting for other risk factors, margin width >2 mm was no longer significantly associated with IBTR risk. | Wapnir, JAMA Surg 2026
