Surgical margins in breast conserving surgery for ductal carcinoma in-situ (DCIS) and clinical outcomes (ODR1819_162)

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The optimal surgical margin in breast conserving surgery for DCIS has not been established. This is in large part due to the absence of accurate surgical and histological margin data. For example the surgical margin currently supported by the American College of Surgeons is based in large part on a study meta-analysis which has multiple weaknesses. The most obvious weakness is that there was no data on the actually surgical margins achieved (as these was not recorded) but rather was based on a margin width which the centre or study had designated as its ‘standard’. The meta-analyses therefore assessed a theoretical margin width and not what the actual margin width that the OFFICIAL2ODR Review Form Part 1A v2 (December 2017)Author: Rachael Brannansurgery achieved.

Patients today therefore arehaving breast conservation surgery for DCIS with margin widths which are not based on data which compared actual margin widths versus clinical outcomes. This audit would aim to provide information of clinical outcomes based on actual surgical margins measured by the pathologistand would represent the most clinically accurate study of its type to date.Project aim:To assess the impact of the size of the width of the tissuebetween the edge of the breast tumour (DCIS) being removed and the edge of the whole surgically excised tissue specimen(known as “margin width”). They wish to establish the optimum margin width for best clinical outcomes. The clinical outcomes assessed would be loco-regional recurrence, distant recurrence and mortality (both overall mortality and breast cancer specific mortality).Data collected by PHE from patients treated by breast conserving surgery for newly diagnosed DCIS will be used to assess whether the size of surgical margins impacts on clinical outcomes such as recurrence rates of DCIS or invasive cancer -either within the treated breast and/or regional lymph nodes or distant metastases –and also on patient survival (both overall survival and breast cancer specific mortality). In addition to the margin width,other parameters which could impact on the analyses would be included. These would include but not be limited to demographic factors (e.g.age, ethnicity, menopausal status, etc) as well as other tumour biological features (e.g.tumour size, grade, presence of microinvasion, hormone receptor status, growth factor status, etc). These other parameters would be included in a multifactor analysis which would produce a more comprehensive and nuanced approach in contrast to the simple observation of margin width effect on clinical outcomes.

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