Close margin <2mm is not associated with higher risks of 10-year local recurrence and breast cancer mortality compared to negative margins in women treated with breast-conserving therapy

Publication date: Available online 13 March 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Susan Tyler, Pauline T. Truong, Mary Lesperance, Alan Nichol, Chris Baliski, Rebecca Warburton, Scott Tyldesley
PurposeThe 2014 SS0/ASTRO consensus suggests "no ink on tumor" is a sufficient surgical margin for invasive breast cancer treated with breast conserving surgery (BCS). Whether close margin <2 mm is associated with inferior outcomes remains controversial. This study evaluates 10-year outcomes by margin status in a population-based cohort treated with BCS and adjuvant radiotherapy (RT).MethodsSubjects were 10,863 women with pT1-T3, any N, M0 invasive cancer referred from 2001-2011, an era in which the institutional policy was to re-excise close or positive margins, except in select cases. All women underwent BCS and whole breast ± boost RT. Local recurrence (LR) and breast cancer-specific survival (BCSS) were examined using competing risk analysis in cohorts with negative (≥2 mm; n=9241, 85%), close (<2 mm; n=1310, 12%), or positive (tumor touching ink; n=312, 3%) margins. Multivariable analysis (MVA) and matched-pair analysis were performed.ResultsMedian follow-up was 8 years. Systemic therapy was used in 87% of patients. Boost RT was used in 34.1%, 76.9% and 79.5% of patients with negative, close, and positive margins, respectively. In the negative, close, and positive margin cohorts, 10-year cumulative incidence of LR were 1.8%, 2.0%, and 1.1%, (p=0.759). Corresponding BCSS estimates were 93.9%, 91.8%, and 87.9%, (p<0.001). On MVA, close margins were not associated with increased LR (HR 1.25, 95% CI 0.79-1.97, p=0.350) or reduced BCSS (HR 1.25, 95% CI 0.98-1.58, p=0.071) relative to negative margins. On matched-pair analysis, close margin cases had similar LR (p=0.114) and BCSS (p=0.100) compared to negative margin controls.ConclusionSelect cases with close or positive margins in this population-based analysis had similar LR and BCSS compared to negative margins. While these findings do not endorse omitting re-excision for all cases, the data support a policy of accepting carefully selected cases with close margins for adjuvant radiation therapy without re-excision.



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