Prediction of positive margins following breast conserving surgery

Positive margins after breast conserving surgery frequently warrant reoperation. Our objective was to evaluate predictors of positive surgical margins after breast conserving surgery (BCS), including a previously validated online calculator/nomogram. Use of reoperation was also evaluated.

Patients with clinical T1-2N0-1Mx-0 primary breast cancer who received standard BCS from 2006 to 2012 were selected (N = 292). Exact Pearson Chi-square test was performed for clinical factors and non-parametric tests were used to evaluate the predictive value of the nomogram for positive margins and re-excision. Spearman's correlation analysis was used to compare actual events vs. nomogram calculations. Multivariate logistic regressions were conducted for multiple variables.

Tumor multi-focality (p = 0.09) and non-ductal histology (p = 0.05), were associated with re-excision; suspicious calcifications (p = 0.08) were associated with positive margins, although no p-value reached statistical significance. The nomogram predicted a median positive margin risk of 20% for cases with and without positive margins. Spearman's correlation analysis for positive margins vs. nomogram calculated positive margin risk was 0.091 (p = 0.121.)

The Breast Conservation nomogram includes several factors associated with positive margins or reoperation, but none of the variables tested were statistically significant on univariate or multivariate analyses. The nomogram's value could not be confirmed, as there was no significant correlation between the calculated risk values and the presence of positive surgical margins.