What are safe margins of resection for invasive and in situ breast cancer?

Adequate surgical margins in breast-conserving surgery are an important predictor of local recurrence (LR) rates. The definition of tumor-free margins in National Surgical Adjuvant Breast and Bowel Project (NSABP) trials requires that tumor cells do not touch ink, but subsequent retrospective single-institution studies have suggested that wider margins confer greater protection against LR. Particularly wide margins have been proposed for ductal carcinoma in situ. However, wider margin requirements lead to higher re-excision rates, with attendant economic, psychological, and cosmetic costs, and perhaps increased mastectomy rates. Juxtaposed against these concerns about optimal margin width, a meta-analysis of clinical trials has demonstrated the survival value of minimizing LR. We are therefore at a juncture where a reduction of LR may be achieved by tumor resection with wide margins, but data regarding optimal margin width are conflicting and the risk/benefit balance of tumorectomy with wide margins has not been demonstrated. A randomized trial of reexcision for close margins inserted into trials of systemic therapy could be considered but seems unlikely. Alternatively, detailed longitudinal data need to balance the value and the cost of wide margins. Until better data are available, the desirable margin width will vary depending on individual circumstances, including age, histology, and patient preference.