A 2 mm tumor free margin minimizes residual disease after BCT
MedWire News: A cancer-free margin of 2 mm from the area of invasive breast cancer is adequate to minimize residual disease in 98% of patients undergoing breast-conserving therapy (BCT), UK researchers report.
The equivalent free margin for ductal carcinoma in situ (DCIS) remains unclear, note the study authors in the International Journal of Clinical Practice.
"Eliminating the possibility of residual disease during BCT is very important as nearly 50% of patients with local recurrence go on to develop secondary breast cancer, which is a progressive incurable disease," said lead author Stephen Ward, from Good Hope Hospital in Sutton Coldfield, West Midlands.
However, the amount of surrounding tissue that should be removed with the tumour, known as the free margin, remains controversial.
"A survey of 200 UK breast surgeons published in 2007 revealed wide variations in what they considered to be an adequate margin, with 24% wanting a clear margin of 1 mm and 65% wanting a margin of 2 mm or more," say Ward and colleagues, who therefore aimed to determine how the size of the margin impacts on the presence of residual disease.
They measured the size of the free margin in 303 breast cancer patients who underwent BCT. Those with a margin of less than 5 mm underwent a wider excision (31%) or mastectomy (13%). The wider excision patients were then assessed for the presence of residual disease.
The researchers report that, in patients with invasive cancer, the proportion of those with residual disease decreased as the margin size increased - from 35.3% with no margin to 2.4% with a margin of more than 2 mm.
In contrast, the probability of residual disease was higher overall for DCIS (33.3% - 57.1%) and did not decline with increasing free margin width. Ward et al suggest that this is because "the full extent of [DCIS] is often non-palpable and is underestimated by mammography making adequate surgical margins more difficult to obtain."
Comparison between the patients with close margins (<2 mm at BCT) and those with clear margins (>2 mm) revealed that tumor size, lobular cancer type (vs ductal), lymphovascular invasion, and nodal involvement were significantly associated with close margins.
Therefore "patients with large tumors and lobular cancer type should be counseled at the time of first surgery concerning the higher risk of further excision and mastectomy," Ward and team conclude.
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By Laura Dean