Analysis of Margin Index as a Method for Predicting Residual Disease After Breast-Conserving Surgery in a European Cancer Center

Abstract

Breast-conserving surgery (BCS), followed by appropriate adjuvant therapies is established as a standard treatment option for women with early-stage invasive breast cancers. A number of factors have been shown to correlate with local and regional disease recurrence. Although margin status is a strong predictor of disease recurrence, consensus is yet to be established on the optimum margin necessary. Margenthaler et al. recently proposed the use of a "margin index," combining tumor size and margin status as a predictor of residual disease after BCS. We applied this new predictive tool to a population of patients with primary breast cancer who presented to a symptomatic breast unit to determine its suitability in predicting those who require reexcision surgery. Retrospective analysis of our breast cancer database from January 1, 2000 to June 30, 2010 was performed, including all patients who underwent BCS. Of 531 patients who underwent BCS, 27.1% (144/531) required further reexcision procedures, and 55 were eligible for inclusion in the study. Margin index was calculated as: margin index=closest margin (mm)/tumor size (mm)×100, with index >5 considered optimum. Of the 55 patients included, 31% (17/55) had residual disease. Fisher's exact test showed margin index not to be a significant predictor of residual disease on reexcision specimen (P=0.57). Of note, a significantly higher proportion of our patients presented with T2/3 tumors (60% vs. 38%). Although an apparently elegant tool for predicting residual disease after BCS, we have shown that it is not applicable to a symptomatic breast unit in Ireland.