Breast conservation in ductal carcinoma in situ (DCIS): what defines optimal margins?

The introduction of mammographic screening has resulted in a rise in detection rate of ductal carcinoma in situ (DCIS); currently accounting for one fifth of screen-detected breast cancers. Although 60-70% of DCIS are treated with breast conserving surgery (BCS) with or without radiotherapy, the frequency of subsequent surgery to re-excise positive margins in order to reduce the probability of recurrences remains high. DCIS recurrence is not only associated with financial, health and psychological implications, around half of these recurrences are invasive disease. An appropriate margin width for patients undergoing BCS for invasive breast cancer has largely been agreed. Although there is a perception that such recommendations may be applicable to DCIS, major differences exist which may affect this application. Importantly, DCIS patients often do not receive systemic adjuvant (endocrine) therapy and not all receive radiotherapy in routine practice. There is evidence that wide margins (i.e. >10 mm) confer better protection against recurrence than positive (i.e. 0mm) margins; however, there remains a debate about the optimum margin width between 0 and 10 mm. Previous studies have demonstrated that radiation therapy may not compensate for lack of re-excision in those patients with positive or close margins whilst wide margins will inevitably compromise cosmesis and patients’ body image perception. This review aims to address the clinical question of the minimal margin width in DCIS treated with BCS that is associated with the lowest recurrence rate and when, therefore, further surgical intervention for re-excision can be safely avoided. A range of clinical circumstances that might affect this are considered. This article is protected by copyright. All rights reserved.