Does intra-operative margin assessment improve margin status and re-excision rates? A population-based analysis of outcomes in breast-conserving surgery for ductal carcinoma in situ.

BACKGROUND AND OBJECTIVES

Using a 2 mm margin criteria, we evaluated the effect of intra-operative margin assessment on margin status and re-excisions following breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS).

METHODS

We identified patients undergoing BCS for DCIS from a prospective, population-based database. Multivariable logistic regression was used to determine the effect of specimen mammography, ultrasound and macroscopic assessment by a pathologist on margins and re-excision rates.

RESULTS

In 588 patients, 52% (95% confidence interval [CI], 48%-56%) had positive margins (<2 mm), 39% (95% CI, 35%-43%) had a re-excision and 15% (95% CI, 12%-18%) had completion mastectomy. There were few re-excisions for margins ≥2 mm (2%). Adjusting for confounders, any margin assessment versus wire localization alone did not reduce positive margins (odds ratio [OR], 0.75; P = 0.202) or re-excisions (OR, 1.14; P = 0.564), however both outcomes varied by type of technique ( P < 0.001). Individually, only macroscopic assessment by pathologist reduced positive margins (OR, 0.54; P = 0.002) and re-excisions (OR, 0.61; P = 0.036).

CONCLUSIONS

Despite adherence to a 2 mm margin criteria, re-excision rates remain high following BCS for DCIS, with 39% converted to mastectomy when re-excision is required. Intra-operative margin assessment does not appear to reduce re-excisions; in particular, surgeons should be aware of the limitations of specimen mammography for margin assessment in DCIS.