Factors predicting residual disease on re-excision after breast conserving surgery.

INTRODUCTION: Breast conserving surgery is the standard of care for early breast cancer, however in a quarter of patients, satisfactory margins are not achieved, usually leading to re-excision. Residual disease is found in less than half of these re-excisions, leading to increased morbidity, poorer cosmesis and increased cost, possibly with no oncological benefit. Our study aimed to identify a group of patients with unsatisfactory margins but a low risk of residual disease, who may be able to avoid re-excision. METHODS AND MATERIALS: All patients from our unit undergoing re-excision for unsatisfactory margins after breast conserving surgery between January 2013 and October 2019 were identified. Pathological factors predicting residual disease were investigated using univariable and multivariable analysis. RESULTS: 220 patients were included. 90 (41 %) had residual disease. Residual disease was more likely in those having mastectomy than cavity shaves (61 % vs 32 %, p < 0.0001). Residual disease increased in a linear fashion with number of involved margins and with increasing tumour size. Tumour size <20 mm (p = 0.045), a pathological to radiological tumour size ratio less than 1.5 (p < 0.0001) and disease-free cavity shaves taken at initial surgery (p = 0.041) were all independent predictors of a low chance of residual disease on multivariable analysis. Patients with all three factors had a 14 % chance of residual disease. CONCLUSIONS: More than half of patients undergo potentially unnecessary re-excision, and patients with small, radiologically obvious tumours are less likely to have residual disease. The decision on re-excision should include these factors in addition to the margin status.

Radiological Underestimation of Tumor Size Influences the Success Rate of Re-Excision after Breast-conserving Surgery.

OBJECTIVE: Failure to achieve adequate margins after breast-conserving surgery often leads to re-excision, either by repeat breast-conserving surgery (BCS) or by mastectomy. Despite the high frequency of this problem, the success rate of achieving adequate margins by repeat BCS is not well documented. The objective of this study was to determine the success rate of repeat BCS and identify the factors influencing that rate. MATERIALS AND METHODS: A retrospective review was performed of all women undergoing repeat BCS for inadequate margins after initial BCS in our breast unit between 2013 and 2019. Univariate and multivariate analyses were carried out to identify the factors influencing how often adequate margins were achieved after repeat BCS. RESULTS: One hundred fifty-four patients underwent repeat BCS after initially inadequate margins, of which adequate margins were achieved in 82%. Patients with successful repeat BCS had smaller tumors, had less underestimation of tumor size on imaging, and were less likely to have had cavity shaves taken at their initial BCS. A tumor size more than 50% larger than predicted by imaging was independently associated with failure of repeat BCS in multivariate analysis (odds ratio: 3.6, 95% CI: 1.41-9.20, p = 0.007). Underestimation of tumor size by imaging was commoner and more extensive in patients with larger tumors and those with ductal carcinoma in situ. CONCLUSION: Re-excision by cavity shaves has a high success rate and should be offered to all patients who are deemed suitable for the procedure. Patients whose tumors are more than 50% larger than predicted by imaging should be counseled about the higher risk of failure.