Reexcision for positive margins in breast cancer: A predictive score of residual disease.

Background: Guidelines recommend re-excision if resection margins are positive in lumpectomy for breast cancer. However, residual disease (RD) is not always found. The aim of our study was to develop a score to predict RD in re-excision specimens.

Materials And Methods: We carried out a multicenter, retrospective study with two population groups. The 'modeling' group was composed of 148 patients treated in the Centre Hospitalier Poissy-St-Germain or the Georges Pompidou European Hospital and the 'validation' group was composed of 67 patients treated in Curie Institute. The score was built with a logistic regression model.

Results: Factors independently associated with RD were: a cumulative length of all positive margins>5 mm, invasion by ductal carcinoma in situ only, a pathological tumor size>30 mm and a pathological tumor size<30 mm with a discrepancy of >50% between pathological and radiological tumor size. The 7-point score allowed the classification of patients into three risk groups for RD: low (16% of patients experienced RD), moderate (65%) and high (100%). The areas under the ROC curve of the score and the logistic model were 0.72(95%CI:0.68-0.75,p = 0.60). The proportion of RD in each group of the validation population (25%, 48%, and 100% in the low, moderate and high group, respectively) confirmed the accuracy of the score in an independent population.

Conclusions: This score enables the identification of patients at high risk of RD but it cannot provide guidance for the decision to undertake re-excision surgery in the low-risk group. Further studies are needed to test the score in extensive datasets and better identify low-risk patients.