Does Mammographic Density have an Impact on the Margin Re-excision Rate After Breast-Conserving Surgery?

Background: Limited and conflicting data exist on an association between mammographic density (MD) and re-excision rates after breast-conserving surgery (BCS). Additionally, the correlation of MD with resection of unnecessary margins during initial BCS is unknown.

Methods: All women with a diagnosis of breast cancer from 2003 to 2012 and enrolled in a larger study on MD were evaluated. Operative and pathology reports were reviewed to determine margin resection and involvement. Mammographic density was determined both by breast imaging-reporting and data system (BI-RADS) classification and by an automated software program (Volpara Solutions). Additional margins were deemed unnecessary if the lumpectomy specimen margin was free of invasive tumor [≥2 mm for ductal carcinoma in situ (DCIS)] or if further re-excision was needed.

Results: Of 655 patients, 398 (60.8%) had BCS, whereas 226 (34.5%) underwent initial mastectomy. The women with denser breasts (BI-RADS 3 or 4) underwent initial mastectomy more frequently than the women with less dense breasts (40.0 vs. 30.5%, respectively; p = 0.0118). Of the patients with BCS, 166 (41.7%) required separate re-excision. Additional margins were taken during BCS in 192 (48.2%) patients, with 151 (78.6%) proving to be unnecessary. In the bivariable analysis, the patients with denser breasts according to BI-RADS classification and volumetric density showed a trend toward requiring more frequent re-excision, but this association was not seen in the multivariable analysis. The rate of unnecessary margins did not differ by breast density. In the multivariate analysis, the re-excision rates increased with DCIS (p < 0.0003) and decreased with resection of additional margins (p = 0.0043).

Conclusions: Mammographic density is not associated with an increased need for re-excision or resection of unnecessary margins at initial BCS.