Abstract P4-03-01: Analysis of the impact of intraoperative margin assessment with adjunctive use of MARGINPROBE® vs. standard of care on margin status with different definitions of positive margin depth, results from a randomized prospective multi center study

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Abstract Background: The current practice of breast conserving surgery (BCS) involves intraoperative margin assessment according to the surgeon's gross assessment and judgment. This intraoperative assessment has been associated with a 20% to 40% reoperation rate to assure negative margins. MarginProbe (Dune Medical Devices, MA, USA) was developed to provide real-time assessment of lumpectomy specimens to evaluate for the presence of disease at the surgical margins. A 21-center international pivotal study was conducted to determine if adjunctive use of MarginProbe can enable surgeons to identify positive margins intraoperatively, resulting in fewer patients who are candidates for re-excision procedures. Results for a 1mm definition of positive margins have been reported previously. We sought to understand the benefit of device use at alternative thresholds. Methods: 664 women with non-palpable lesions undergoing lumpectomy for DCIS and invasive cancer were enrolled and 596 randomized (1:1) in the operating room following standard of care (SOC) lumpectomy. In the device arm, MARGINPROBE was used to assess all surfaces of the lumpectomy specimen and positive readings required additional resections. The device was not used on additional resections. All specimens were examined to verify excision of the target lesion intraoperatively. Pathologists were blinded to study arm. Additional surgeries to re-excise involved margins were performed per each individual site criteria. Patients were followed for 2 months following surgery; additional procedures were documented. Distance from tumor to each margin face was recorded for each patient. Results: Following lumpectomy, the number of patients having positive margins due to failed intraoperative assessment was significantly reduced in the device arm at each potential definition of positive margins. Patients with positive margins after 1st surgeryDepthDevice (%) N = 298Control (%) N = 298p-value0mm6.413.40.00571mm15.438.3<0.00012mm22.549.7<0.00013mm30.957.0<0.00014mm36.661.7<0.00015mm39.966.4<0.0001*excludes positive margins on shavings, as device was only used on the main specimen Conclusions: It has been shown previously that adjunctive use of MARGINPROBE significantly reduced the number of candidates for re-excision at a 1mm definition of positive margins. Based on this analysis, surgeons can expect a substantial reduction in the number of patients with positive margins at definitions from tumor on ink to 5mm. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-03-01.