Close/positive margins after breast-conserving therapy: additional resection or no resection?

The primary goal of breast conserving surgery or mastectomy is the prevention of recurrent breast cancer. The distinguishing goal of breast conserving surgery is preservation of a breast as normal in appearance as possible. If the margins of the excised breast cancer extend to the border of the excised specimen one cannot determine the amount of gross tumor that was not excised. Retrospective analyses of surgical series show a 2-3 fold increase in local recurrence of the breast tumor if the margin is positive under the microscope, even when the surgeon believed it to be clear on gross examination. This fact has led to a variety of techniques attempting to ensure that the margins of the excised specimen are free of obvious tumor including pre-operative and specimen imaging and mapping, neo-adjuvant therapy to shrink the primary tumor, touch-prep and frozen section of the specimen margins during the procedure, shaving additional margins about the specimen at the closest aspects grossly or on all six surfaces, and examinations of the in situ walls of the remaining breast with new instrumentation. An obvious approach to diminishing the likelihood of positive specimen margins is taking a wider margin of normal tissue. As the volume of resected breast increases by the cube of the radius of excised tissue, this tracks all too well with diminishing cosmetic results and patient approval of the conserved breast. The question posed regards the finding of a positive or close margin after the surgical procedure. The finding of a positive margin can be parsed to a microscopic focus of tumor at the margin vs. the margin inking on a tumor surface. The latter demands re-excision despite the morbidity involved barring an extraordinary contra-indication or patient refusal. It represents the very real possibility of sufficient residual gross tumor in the breast that even with systemic therapy and breast irradiation the tumor will be un-controlled. A microscopic focus separated from the bulk of the primary tumor and adjacent to a margin has not been shown to carry such risk. The margin of normal tissue beyond the primary tumor that significantly reduces the risk of local recurrence remains undefined. Sufficient data are available to say that in the era of systemic therapy, excellent radiation therapy techniques, and boost doses when indicated, no margin of normal breast tissue beyond the tumor has been shown to be clearly superior to a layer of cells between the ink and the tumor. The larger the tumor and the more aggressive its biology is judged to be the lower the confidence that a single layer of cells at the point of histologic study accurately represents a clear margin. As in all medical decisions wise judgment must integrate all of the known factors to reach the best recommendation. There are few circumstances that would warrant a second surgical procedure for a close but clear margin today.