Abstract P2-12-12: MarginProbe device use and re-excision rates for breast conservation surgeries

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Abstract Background: Current methods of intraoperative assessment of lumpectomy margins are limited. Previous studies have found a lower rate of re-excisions with the adjunctive use of the MarginProbe device (Dune Medical Devices Ltd, Israel). The purpose of this study was to compare the tumor characteristics and re-excision rates before and after the use of MarginProbe for patients who had breast conservation surgery (BCS) at our institution. Methods: The Breast Cancer Database of our medical center was queried for patients who underwent BCS from 1/2010-3/2015 by three breast surgeons. 2 surgeons used the MarginProbe to direct excision of additional margins at the time of primary lumpectomy surgery and 1 surgeon performed routine 6-surface cavity shavings. We compared our historical data (1/2010-12/2014) to MarginProbe data (1/2015-4/2015). The following variables were included: age, mammographic breast density, tumor characteristics, and re-excision rates. Statistical analyses were performed using Pearson's Chi-Square and Fisher's Exact Tests. Results: We had a total of 1201 women who had BCS among the 3 breast surgeons. The median age was 61 years. The median invasive size was 1.2 cm. Majority of cancers were early stage (stage 0, I), invasive ductal carcinoma (61%), ER-positive (86%), PR-positive (74%), and Her2Neu-negative (88%). These tumor characteristics were not statistically different in the pre- and post-MarginProbe groups. The majority of patients had dense breasts (51%) and density did not differ among the pre- and post-MarginProbe groups (p=0.86). For the surgeons who used the MarginProbe for margin assessment at the time of surgery, the re-excision rate fell from 17% to 0% and 35% to 20% during the 4-month period. In contrast, the surgeon who routinely performed 6-surface shavings had a re-excision rate that fell from 13% to 12% in the same time period. 88% of MarginProbe readings were false positive. There was one false negative reading. Table 1. Tumor CharacteristicsVARIABLESTotal N=1201%No MarginProbe (N=1144, 95%)%MarginProbe (N=57, 5%)%P-valueTUMOR STAGE0292242782414240.95I64454614543053 IIA, IIB22319211191221 IIIA, IIIB, IIIC39338312 IV30.330.300 HISTOLOGYDuctal carcinoma in situ305252892516280.75Invasive ductal carcinoma73061695613561 Invasive lobular carcinoma1129107959 Invasive other54553512 ESTROGEN RECEPTOR STATUSNegative16314157146110.46Positive101486963865189 PROGESTERONE RECEPTOR STATUSNegative307262942613230.56Positive86774823744477 HER2-NEU STATUSNegative788887538835810.22Positive92108610614 Equivocal19217225 Conclusions: Routine use of the MarginProbe device was associated with lower re-excision rates compared to historical data and concurrent 6-cavity shaving approach. Better intraoperative margin assessment and lower re-excision rates will decrease the burden of breast cancer on patients and the health care system and support the practice of breast conserving surgery. Citation Format: Schnabel F, Guth A, Axelrod D, Chun J, Schwartz S, Shapiro R. MarginProbe device use and re-excision rates for breast conservation surgeries. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-12-12.