The ideal margin width after mastectomy has been debated, but the definition of a negative margin for invasive cancer as used in the National Surgical Adjuvant Breast and Bowel Project (NSABP) trials and recommended in the recent SSO Consensus Panel was no invasive tumor at the inked margin. Other randomized trials did not specify margin status or used grossly negative.
A recent consensus conference sponsored by the SSO, ASTRO, and CAP reviewed the literature and concluded that no tumor on ink is an adequate margin for breast-conserving surgery and radiation.
Shave margins appear to be the most efficient way to examine margin status and determine need for reoperation.
The width of margins for ductal carcinoma in situ (DCIS) is more hotly debated.
A patient treated with BCS and a pathology report showing a T2N0(i+) breast malignancy that is triple negative should be evaluated in a multidisciplinary approach, so a medical oncologist and a radiation oncologist are important in the evaluation of this patient. Even if the patient chose to have mastectomy, a referral to a medical oncologist is indicated. Isolated tumor cells are not a reason to perform ALND.
ER(-) patients should not have Oncotype testing. Patients with node-negative, ER-positive cancer are the most likely to benefit from multigene expression-based prognostic tests. In contrast, adjuvant chemotherapy remains a standard recommendation for patients with T2N0 cancers that are ER-negative, PR-negative, and HER2-negative or are HER2-positive.
Several multigene prediction assays are commercially available (Oncotype Dx; Mammaprint, and PAM50), but only Oncotype Dx has level 1B evidence to support its use in predicting benefit of adjuvant chemotherapy. This genomic profile was tested using tumor tissue from patients treated on a randomized clinical trial comparing tamoxifen to tamoxifen plus chemotherapy. The other genomic assays provide good prognostic information but were not well validated. However, clinical trials are underway to validate each of these tests in randomized patient samples. The decision to order a multigene assay test is usually left to the medical oncologist to determine whether or not the test is indicated. If a patient is not willing to accept a recommendation of adjuvant chemotherapy, the information from the test will not be useful.
At times a surgeon can order the multigene assay so that the information is available to the oncologist at the time of the visit, but it is important that the surgeon and medical oncologist communicate as to which patients should have this test performed so that the information is useful to the patient and the multidisciplinary team.
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Moran MS, Schnitt SJ, Giuliano AE, et al. Society of Surgical Oncology-American Society for Radiation Oncology consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in Stages I and II invasive breast cancer. Ann Surg Oncol. 2014;21:704-716.