Effect of margin width on local recurrence in triple-negative breast cancer patients treated with breast-conserving therapy.

BACKGROUND: The effect of increasing negative margin width after breast-conserving therapy (BCT) on local recurrence (LR) is controversial. LR rates vary by subtype, with the highest rates seen in triple-negative breast cancer (TNBC). This study examined LR rates in relationship to margin width in TNBC treated with BCT. METHODS: Women with TNBC who underwent BCT between 1999 and 2009 were identified. Margins were defined as positive (ink on tumor), 0.1-2.0, and 2 mm. Patients with positive margins were excluded. Statistical comparisons were by t test, Fisher's exact test, and Wilcoxon rank sum test. Cumulative incidence of LR was compared by competing-risks methodology. RESULTS: Of 535 cancers, 71 had margins ≤2 mm and 464 had margins >2 mm. At a median follow-up of 84 months (range 8-165 months), there were 37 local, 18 regional, and 77 distant recurrences or deaths as first events. Ten patients had a locoregional recurrence before planned radiotherapy and were excluded from cumulative incidence analyses. The cumulative incidence of LR at 60 months for margins ≤2 mm was 4.7 % (95 % confidence interval 0-10.0) and for >2 mm was 3.7 % (1.8, 5.5) (p = 0.11). After controlling for chemotherapy and tumor size, there was no difference in LR between the two margin groups (p = 0.06). A difference in the risk of distant recurrence or death was not observed (p = 0.53). CONCLUSIONS: Margin width of >2 mm was not associated with reduced LR rates. These data support a negative margin definition of no ink on tumor, even in this high-risk TNBC cohort.

Duke Scholars

Author Alice Yoosun Ho Radiation Oncology