Completion mastectomy after breast conserving surgery.

ABSTRACT

BACKGROUND: Breast conserving surgery (BCS) is increasingly offered to suitable patients diagnosed with early stage breast cancer. Occasionally the pathological margins on specimens following BCS are positive. The objective of this study is to assess the proportion of patients within our unit who required completion mastectomy after BCS and to determine if predictive factors could be identified to assist the breast surgeon identifying those patients at risk of positive margins following BCS. METHODS: All patients diagnosed with breast cancer between 2001 and 2005 were reviewed. Patients undergoing BCS had their histopathological specimens examined for any evidence of residual tumour at the margins of the resected specimen. These patients then proceeded to completion mastectomy if these margins were positive for residual tumour. Multinominal logistic regression was then performed on clinico-pathological factors for each of these patients to determine if predictive factors existed for determination of residual disease in the mastectomy specimen following BCS. RESULTS: Logistic regression demonstrated that size of the initial tumour was the only significant predictor for the presence of completion mastectomy residual carcinoma (CMRC) (p=0.014) and that tumours with an initial size > 2.5 cm were 15 times more likely to have a CMRC than tumours < 1.5 cm. This prediction model based on the initial tumour size had an 89.5% specificity and 52.2% sensitivity. The odds ratio for CMRC based on histological tumour type for each additional 1cm increase in size of the initial tumour was 2.82 for ductal carcinoma in situ, 2.60 for infiltrating ductal carcinoma and 2.26 for other tumours. CONCLUSION: This study demonstrates that residual disease in total mastectomy specimens following BCS increases significantly with increasing original tumour size. With current data, surgeons can inform patients of the risks of residual cancer associated with BCS with a view to increase the rate of primary mastectomies in those patients with presenting tumours greater than 2.5 cm.