Importance of routine cavity sampling in breast conservation surgery

Background: The role of cavity biopsy (CB) at the time of wide local excision (WLE) for primary breast cancer has not been evaluated fully. This study compared four groups of patients to determine the significance of margins and CB histology on tumour characteristics and outcome. Methods: This was a retrospective study of patients undergoing WLE and CB in one institution over 21 years. Demographic data, tumour characteristics and survival information were obtained. Four subgroups of patients were compared according to their margin and cavity status (positive or negative). Results: A total of 957 patients had WLE. The median 10-year survival was 85.6 per cent and breast cancer-specific survival was 92.4 per cent. Tumour size, grade, node and oestrogen receptor status were independent predictors of survival. There was poor concordance between positivity of resection margins and CB (32.0 per cent); a negative margin carried a 10.8 per cent risk of demonstrable residual disease. A positive CB, but not a positive margin, was associated with reduced overall survival and breast cancer-specific survival. Conclusion: Cavity status was more significant with regard to survival than margin status. CB is important in identifying residual and multifocal disease, as margin and cavity positivity are often not concordant.