Margin assessment by cavity shaving after breast-conserving surgery: analysis and follow-up of 543 patients

Aims: To analyse cavity shaving as a method of assessing completeness of surgical excision after breast-conserving surgery. Methods: Shavings were taken from the wall of the cavity remaining in the breast after breast-conserving surgery in 543 women. Each shaving was extensively sectioned and the presence and type of microscopic disease recorded. Disease in cavity shavings (tumour bed positivity) was correlated with clinicopathological factors as well as overall survival. Results: Tumour bed positivity (TBP) was found in 37% of patients (16% with invasive disease). Patients were selected for further surgery according to the extent of positivity, which varied widely. A total of 15% of patients underwent re-excision or mastectomy. TBP was significantly associated with high tumour grade, presence of an extensive intraduct component, young age and large tumour diameter. It was also associated with a significantly shorter overall survival when compared to patients who were tumour bed negative. Conclusions: Cavity shaving is a practical and sensitive method of assessing completeness of excision after breast-conserving surgery. In addition it may provide useful prognostic information.