Published MarginProbe (MP) data reports ≥50% reduction in positive lumpectomy margins. Standard of care (SOC) in our facility uses intraoperative pathologic gross assessment for invasive cancer. We sought to determine if adjunctive use of MP would provide incremental value over gross assessment alone.
This is a single-site, single-surgeon retrospective chart review of 86 consecutive lumpectomies with MP from 12/2018–11/2019. Margins were considered positive using SSO/ASTRO “no ink on tumor” consensus guideline for invasive cancer, and SSO/ASTRO/ASCO consensus guideline of 2mm or greater for pure DCIS. Significance was measured using Fisher’s exact two-tailed test.
76 patients (7 bilateral, 3 unilateral/multi-focal) yielded 86 lumpectomies for inclusion. Mean age was 69.8 and mean tumor size was 1.09cm. 68 invasive cancers were assessed using adjunct MP and gross assessment while 18 DCIS cases utilized MP only. Among all cases, gross assessment alone reduced positive margins from 27.9% to 19.8% (29.2% relative reduction, p=0.28). Utilizing both modalities in tandem, positive margins decreased from 27.9% to 9.3% (66.7% relative reduction, p<0.01) representing a 46.9% relative reduction versus gross assessment alone.
Main specimen tissue volume was 27.1cc. After gross assessment and MarginProbe evaluation, there was additional excised volume that averaged 2.9 cc. Total averaged excised volume was 33 cc. This compares to the reported 40-60 cc average in multiple studies.
Adjunctive use of MP with gross assessment maximizes reduction of positive margins during breast conserving surgery while minimizing impact on specimen volumes.