Surgical margins and risk of locoregional recurrence in invasive breast cancer: an analysis of 10-year data from the Breast Cancer Treatment Quality Assurance Project.

AIM There is debate as to what constitutes an adequate excision margin to reduce the risk of locoregional recurrence (LRR) after breast cancer surgery. We have investigated the relationship between surgical margin distance and LRR in women with invasive breast cancer (IBC). METHODS Tumour free margin distances were extracted from histopathology reports for women with IBC, treated by either breast conserving surgery or mastectomy, enrolled in the Breast Cancer Treatment Group Quality Assurance Project from July 1997 to June 2007. Cox proportional hazards regression analyses were conducted to compare the risk of LRR for involved margins compared with negative margins, measured in increments rounded to the nearest mm. RESULTS 88 of 2300 patients (3.8%) experienced an LRR after a mean follow-up of 7.9 years. An involved margin, or a margin of 1 mm was associated with an increased risk of LRR (HR 2.72, 95% CI 1.30-5.69), whilst margin distances of 2 mm or greater were not. Risk of LRR with margin distances <2 mm was particularly high amongst those not receiving radiotherapy (RT). CONCLUSION Based on our findings, we recommend that a tumour free margin distance of 2 mm be adopted as an adequate margin of excision for IBC, in the setting of patients receiving standard adjuvant RT and adjuvant drug therapies as dictated by the current clinical treatment paradigms.