Importance of margin width in breast-conserving treatment of early breast cancer

BACKGROUND AND METHOD: The association between margin width and ipsilateral breast tumour recurrence (IBTR, defined as invasive recurrence) was investigated in a population-based nationwide cohort of 11,900 patients undergoing breast-conserving therapy for invasive cancer.

RESULTS: The median follow-up was 4.9 years. The cumulative incidence of IBTR at 5 and 9 years was 2.4% and 5.9%, respectively. A final positive margin increased the risk of IBTR (HR 2.51; 95% CI 1.02-6.23). No decrease in IBTR with a wider negative margin compared to a narrow but negative margin was observed in the adjusted analysis of margin width (>0 to <2 mm vs. ≥2 to <5 mm vs. ≥5 mm (reference): HR 1.54 (CI 95% 0.81-2.93) vs. 0.95 (CI 95% 0.56-1.62) vs. 1). However, few patients had narrow margins. The factors associated with increased IBTR were young age (P < 0.001), >4 positive lymph nodes (P = 0.008) and re-excision (P = 0.003). A reduced risk of IBTR was observed with chemotherapy (P < 0.001), boost radiation (P = 0.023) and ER positivity (P < 0.001).

CONCLUSION: An overall low rate of IBTR was observed. A final positive margin was associated with a more than twofold risk of IBTR. There was no evidence for better local control with wider margins, but the data were insufficient to show whether narrow margins were as good as wider negative margins in terms of local control. J. Surg. Oncol. 2016;113:609-615. © 2016 Wiley Periodicals, Inc.