Background: Surgical margins in breast conserving surgery (BCS) of ductal carcinoma in situ (DCIS) as well as invasive cancer are a subject of intense discussion. A positive margin is still one of the strongest predictor for risk of local recurrence of intraductal and invasive breast cancer. Intraoperative margin assessment of DCIS is difficult and existing options are unsatisfying.

Aim of our study was to evaluate the performance of MarginProbe®(Dune Medical Devices, Boston, MA, USA) in assessing surgical margins for DCIS and the contribution to lowering the re-excision rate after initial BCS.

Material and methods: The device includes a disposable hand-held probe and a console, is based on radiofrequency spectroscopy, and detects differences in dielectric properties between normal and malignant breast tissue.

The multicentre single arm, post market study was performed on 55 patients at 3 German sites under approval of institutional review boards. MarginProbe® was used as an adjunctive tool to the current practice. All specimens were sent for paraffin embedded pathological analysis.

The procedure success was defined as both: negative margins after initial BCS; and early identification of an extended lesion, with conversion to mastectomy instead of performing a re-excision BCS.

Results: From September 2009 - May 2010, 42/55 patients were eligible for this analysis. In comparison with a historical re-excision rate of 39% for DCIS patients undergoing BCS, use of MarginProbe® led to a reduction of the re-excision rate by 56%, down to 17% (p = 0.018) (surgical margin width of 5 mm). The procedure success was also significantly improved by more than 3-fold (p<0.0001), from 14% (6/42) by standard of care (SOC) alone, to 57% (24/42) with use of the device. In 21% (9/42) of the cases use of the device led to a direct conversion to mastectomy due to extensive disease identified, sparing an additional re-excision BCS. Resected average main specimen tissue volume was 34.6 cc. Tissue volume associated with false positive margins was, on average, 7.5 cc per patient. Cosmetic outcomes were not different.

Discussion: In synopsis with the other two clinical trials (MAST and US pivotal study) we found our data consistent. Each trial reported a reduction of the re-resection rate by more than 50%.

Our results demonstrate that adjunctive use of the device is effective in achieving procedure success and reducing re-excisions for DCIS patients. Several options for intraoperative margin assessment exist, but for DCIS they are time-consuming and insufficient (frozen section, touch prep cytology) or experimental (near-infrared fluorescence optical imaging, high-frequency ultrasound). Usually, the pathologist provides final analysis of the lesion extension and margin assessment several days after operation.

Conclusion: MarginProbe® is a device that provides a fast and effective technique for intraoperative margin assessment that is already used in daily routine. It lowers the re-excision rate for both DCIS and invasive cancer significantly, by >50%, without any influence on patient's cosmesis. It may allow the surgeon to perform oncoplastic or reconstructive breast surgery and IORT more safely in the future.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-18-14.