Intra-operative assessment of excised breast tumour margins using ClearEdge imaging device

J Michael Dixon1, OBE FRCS, Lorna Renshaw1, RGN, Oliver Young1, FRCS, Dhananjay Kulkarni1, FRCS, Talha Saleem1, FRCS, Moshe Sarfaty2, PhD, Ramaswamy Sreenivasan2, PhD, Catherine Kusnick2, MD, Jeremy Thomas1, FRC Path, Linda Williams3, PhD

Institutions:1. Edinburgh Breast Unit, Western General Hospital, Edinburgh, Scotland2. LS BioPath, Mountain View, California, United States3. University of Edinburgh, Medical School

Address for correspondence: Professor J Michael DixonEdinburgh Breast UnitWestern General HospitalEdinburghEH4 2XUEmail: mike.dixon@ed.ac.ukTel. +44131 537 2643

2

Abstract

Introduction

Breast conserving surgery (BCS) aims to remove a breast cancer completely and obtain clear

margins. Complete excision is essential to reduce the risk of local recurrence. The ClearEdge™

(CE) imaging device examines margins of excised breast tissue intra-operatively. The aim of this

study was to investigate the potential of the device in detecting margin involvement in patients

having BCS.

Methods

In Phase-1 58 patients underwent BCS and had 334 margins assessed by the device. In Phase-2

the device was used in 63 patients having BCS and 335 margins were assessed. Patients with

margins considered close or involved by the CE device were re-excised.

Results

The margin assessment accuracies in Phase-1 and Phase-2 compared to permanent section

pathology were very similar: sensitivity (84.3% and 87.3%), specificity (81.9% and 75.6%),

positive predictive value (67.2% and 63.6%), and negative predictive value (92.2% and 92.4%).

The false positive rate (18.1% and 24.4%) and false negative rate (15.7% and 12.7%) were low

in both phases. In Phase-2 re-excision rate was 37%, but in the 54 where the CE device was used

appropriately the re-excision rate was 17%. Had all surgeons interpreted all images appropriately

and re-excised margins detected as abnormal by the device in Phase-2 then the re-excision rate

would have been 7%.

Conclusion

This study shows that the CE device has potential to reduce re-excision after BCS and further

randomized studies of its value are warranted.

3

Introduction

Breast conservation surgery (BCS) is the standard treatment of choice for the majority of women

diagnosed with early stage breast cancer [1-3]. BCS involves the removal of malignant tissue

with a surrounding margin of normal breast tissue. Having orientated the excised specimen, the

surgeon sends it together with any additional margin shavings and following a thorough

microscopic evaluation that takes several days, a report on the margin status is issued. The

likelihood of local recurrence following BCS is linked to the status of the margins [4, 5]. Data

from 2 meta-analyses show that clear margins of ≥1 mm reduce the risk of cancer recurrence [6,

7]. In the US about 250,000 patients undergo BCS annually. In BCS the range of re-excision to

clear involved margins varies between 20-70% [8-13]. These second or even third additional

surgical procedures add to the morbidity of BCS, adversely affect cosmesis [14], and add

significant costs. There is a need for new technologies that detect involved margins during

surgery, and allow the surgeon to remove all malignant tissue during one BCS procedure.

There are two possible approaches to Intra-Operative margin assessment. One option is to

examine the surfaces of the resection cavity in vivo but this is extremely challenging for a variety

of reasons. The second and more practical approach is to assess the margins of the resected

specimen. Current intraoperative methods for margin assessment include gross evaluation of the

tumor specimen [8], intraoperative ultrasonography, specimen slice radiography [15, 16], and

pathologic evaluation either with touch preparation cytology or frozen section. The

MarginProbe™ [17] uses radiofrequency reflection to locally assess margin involvement.

4

The ClearEdge™ (CE) is a handheld portable imaging device that differs from currently

available devices in that it uses bio-impedance spectroscopy that is very sensitive to extracellular

and intracellular variations of tissue dielectric properties. This new imaging modality enables

surgeons to identify and localize areas of abnormal tissue at a margin based on their dielectric

properties. Tissue abnormalities detected by the device include DCIS, invasive cancer, and also

includes abnormalities such as atypical ductal and lobular hyperplasia, lobular carcinoma in situ,

and areas of increased cellularity associated with inflammation. The aim of the current study was

to demonstrate the safety and accuracy of the CE device and determine its potential to reduce re-

excision rates in patients undergoing BCS in a two phase clinical study.

Patients and Methods

The CE imaging device used in this study is a battery operated, portable, hand-held imaging

device equipped with a sterile single-patient head [Figure 1], and a docking base for battery

charging. The device is docked in a charging cradle between operations. The single use head and

drape were provided sterile and can be attached to the reusable handheld device in the sterile

field of the operating room. A unique feature of the CE is that a baseline measurement is made

on each patient’s normal breast tissue. Having baselined the device the surgeon uses the device

to scan all margins of the excised tissue and any other cavity margin shavings. The CE head’s

tissue penetration depth guard was set to a depth of 3mm in an effort to ensure that the margins

of the excised tumor were free from any residual cancer to a depth of 3mm. A penetration depth

of 3mm in fresh tissue typically corresponds to about 2 mm of fixed tissue as reported by the

pathologist. Each scan produces a color-coded image on the device’s LCD display. [Figure 2].

After each margin of the excised tissue is scanned the surgeon can decide intraoperatively if re-

5

excision of additional tissue from that margin is required. This study was performed in two

phases.

Phase-1: This phase of the study was designed to validate the safety and accuracy of the CE

imaging device when used ex-vivo to image the margins of excised wide local excision

specimens. In Phase-1 58 patients were enrolled and the clinical and pathological features of

these patients and their cancers are summarized in Table 1a [Table 1a]. BCS was performed by

nine different surgeons in the Edinburgh Breast Unit.

The excised specimen was first subjected to intraoperative X-ray imaging. The Faxitron®

produces an image of the entire excised specimen to determine first the mammographic lesion

has been excised and second does not extend to any imaged radial margin. Additional margin

shavings were removed in 34 patients (59%) based on examination of the specimen X-Ray.

Assessment of the margins based on an X-ray image was documented on a clinical research

form. After surgery had been completed the CE device was used to image each margin of the

excised tissue specimen. All margins were scanned completely using the device generating

multiple images per margin. Assessment of each margin based on CE images was performed and

documented by the operating surgeon on a specific clinical research form. Any location

identified as abnormal by the device was marked on the specimen using orange ink so the

pathologist could assess this area in detail. A margin was deemed abnormal based on the CE

image when at least one of the images taken from that margin was assessed as abnormal. Six

margins (anterior, posterior, superior, inferior, medial and lateral) were assessed in each patient.

In Phase-1, as the margins were assessed by the CE device after the operation had been

6

completed, no patient with a margin that was abnormal on CE imaging had re-excision based on

the result.

The accuracy of both CE and X-Ray images assessments were compared to permanent section

pathology. The potential of CE to reduce re-operation rate was based on the surgeon’s

assessment of the CE image of each margin and correlating this with the need for re-excision

based on permanent section pathology. If the pathologist identified DCIS or invasive cancer

within 1mm of the final radial margin then re-excision at a second operative procedure was

performed. It was assumed that had the surgeon acted on the basis of an abnormal CE image and

re-excised the abnormal margin, that later re-excision may have been avoided. The potential

reduction in the rate of re-operations based on CE imaging was compared to the actual re-

operation rate.

Phase-2: In this phase, the CE device was used intraoperatively by each surgeon in an attempt to

reduce the reoperation rate. In this phase surgeons used the CE device on excised and oriented

specimens in real time and documented their assessment and actions on a clinical research form.

Surgeons also used X-ray images and documented their assessment of the specimen radiographs

on a separate from. Unlike in Phase-1, the surgeon was asked to interpret the CE images and to

perform re-excision of any margin in which the imaging was abnormal. 63 patients were enrolled

in this study [Table 1b] and ten surgeons used the device and performed further margin excisions

based on the results obtained with either CE or X-ray. Of 63 patients enrolled in the study in only

54 cases was the CE device used as per protocol.

7

Complete excision was defined as achieving clear radial margins of both invasive cancer and

DCIS by greater or equal to 1mm. The actual reduction in the reoperation rate by the CE device

was calculated by first determining the number of patients in which further margins were excised

based on the CE and this cleared a margin that would otherwise have necessitated re-excision.

Images were reviewed blind by JMD. It was clear that in 9 patients the device was not used

appropriately as the images were incomplete; these patients were classified as protocol violations

and were removed from the calculation of reoperation rate. It was also noted that on review in

some of these 9 patients abnormalities were present at one or more margin but the surgeon failed

to re-excise. These nine patients were removed from calculations of re-operation rates given that

the device was not used as per protocol. In a further group of 5 patients it was evident that the

surgeon had not taken an appropriate baseline image.

Results

Table 2 summarizes the accuracy results of Phase-1 (58 patients) and Phase-2 (63 patients) using

CE and X-ray imaging. In Phase-1 and Phase-2, 334 and 335 margins were measured with the

CE device, and 351 and 338 margins were assessed by X-Ray, respectively. [Table 2a] [Table

2b] The reason that not all margins were assessed by the device was that in Phase-1 some

patients surgeons reported some of the margins were disrupted, or the margin was too small to

maintain proper contact between the device and the breast tissue and in Phase-2 in nine patients

imaging of the margins were incomplete. The 351 margins assessed by X-Ray included a number

of re-excisions performed based on specimen radiography. The results demonstrate that CE has

a higher sensitivity in Phase-1 than specimen X-Ray.

8

Re-operation rates achieved using only X-Ray images are compared to those potentially

achievable based on the CE images in the 2 phases of the study are shown in Table 3 [Table 3].

Potential re-operation rates are provided as in Phase-1 the device was used after surgery was

completed. 17 of 58 patients had re-operation for involved margins in Phase-1: a rate of 29%.

Had the surgeon excised margins that were identified as involved based on the CE image in

Phase-1 then only 6 out of 58 patients would potentially have required re-excision, a re-operation

rate of 10%. The results obtained by the CE were deemed satisfactory to proceed to Phase-2 of

the study.

Results of Phase-2 of the study are shown in in Table 3. The re-operation rate obtained with the

CE device is compared to that obtained by using X-Ray images. 63 patients’ specimens had

specimen radiology and the reoperation rate based on this alone was 37%. The CE device was

used correctly per protocol only in 54 patients and, 9 patients in this group had a re-excision: a

rate of 17%. In 5 of the 54 patients who had re-excision the surgeon did not baseline the CE

properly on the patient’s specimen. This included 2 patients where the surgeon baselined the

device on malignant tissue and 3 where the baseline was on fat tissue. This was evident from

review of the images stored on the device. When the baseline is set on a malignant or fibrous

tissue, the images from all margins are uniformly deep green pixels with no other color pixels.

When the baseline is set on a fat tissue then the images of all margins show a majority of red

pixels. This leaves 49 patients in whom the device was used as per protocol and baselined

appropriately and in this group the re-excision rate was only 4/49 (8%). The CE device had no

effect on margin assessment by the pathologist.

9

Discussion

The challenge of BCS is to remove the invasive cancer and or DCIS to clear margins while at the

same time limiting the volume of excision to leave a satisfactory cosmetic result. The definition

of what constitutes a clear margin has been the subject of 2 meta-analyses and a recent

Consensus statement [7, 18, 19]. Studies have shown that close margins increase local recurrence

rates (OR 1.74) and two meta-analyses [7, 19] have demonstrated that when looking at different

thresholds for negative margins ≥1mm is as good as wider margins. The data on >0mm were

insufficient in the second analysis as minimal data on this margin were included in the meta-

analysis [7] The consensus panel decided to recommend no cancer on ink as a negative margin

[18]. In the UK 1mm is the most widely used width for the definition of a clear margin as this is

the margin width that is most consistent with the conclusion reached by the two meta-analyses.

1mm is the margin that was used in this study.

Historically, re‐excision rates have ranged from 31% to 46% [9, 20, 21] for DCIS alone and from

11% to 46% for invasive breast cancer with DCIS [22-26]. A variety of intraoperative

technologies have been used to assess the surgical margin to allow targeted re-excision at the

same operation, including frozen section analysis [27], touch preparation (imprint) cytology [28],

near infrared (NIR) fluorescence optical imaging [29], x‐ray diffraction [30], high‐frequency

ultrasound [31], micro‐CT [32], MRI of the specimen and the MarginProbe™ [33]. Optical

breast imaging uses near‐infrared (NIR) light to assess optical properties of tissue and has a high

reported sensitivity [34, 35]. Another promising approach is the use of high‐frequency (HF)

10

ultrasound. [36, 37]. X‐ray diffraction (XRD) is based on alterations in tissues following

invasion by cancer. A micro‐CT and mini MRI systems have also been developed to look at

margins [30]. The MarginProbe™ measures electrical reflection properties of the breast tissue

using radiofrequency (RF) spectroscopy. RF signals are delivered and acquired by the probe. It

takes approximately 5 minutes to use the device on the excised tissue specimen. Results so far

are promising but it requires further studies to demonstrate its cost-effectiveness. [17, 38-41]

The CE imaging device was developed to examine the margins of excised breast tissue intra-

operatively and differs from any currently available device in that it uses bio-impedance

spectroscopy that is very sensitive to extracellular and intracellular variations of tissue dielectric

properties. It has a coloured display and each pixel in the image is coloured greens (fatty no

cancer), yellows (fibrous no cancer) and reds (cancer or cellular abnormality close to margin).

Green and yellow pixels are considered as characteristic of normal tissue and reds are abnormal

tissue. It has shown in this study that it is safe and that surgeons can be trained in its use. In

Phase-1 of the study nine surgeons used the device in 58 patients undergoing breast conserving

surgery for invasive or in situ breast cancer. Each surgeon had training on only 1 or 2 cases prior

to the study and all were able to use the device and get recordable images during the study.

Based on surgeons’ assessments in Phase-1 of this study, we showed that the device has a high

sensitivity for involved margins while at the same time having a low false positive rate. Based on

these results, it was estimated the device had the potential to reduce the rate of re-excision below

10%. The results using the CE device were much better than those obtained with specimen

radiography. This is not surprising as our recent study has shown that DCIS is frequently not

visible on conventional imaging and that is the main reason for surgeons incompletely excising

11

cancers [42]. As much of the DCIS is not visualized by mammography or ultrasound, it is

unlikely that techniques that rely on X-rays or ultrasound including intraoperative ultrasound will

decrease re-excision rates. That is why new techniques are required to increase the rates of

complete excision.

A unique feature of the CE device is the capability to automatically adjust its baseline to the

individual patient’s breast tissue, thus potentially enhancing its detection sensitivity for each

individual patient. The patient’s specific baseline is generated by an initial reading taken on

normal breast tissue away from the tumour site. Typically, a proper baseline will display a

combination of green and yellow pixels at the initial image. Failure to take an appropriate

baseline is identified from consecutive images. If the images of the margins show only deep

green pixels then most likely the device has been baselined on fibrotic or malignant tissue. If all

the consecutive images on all margins show many red pixels then the device was baselined on

fatty tissue. In such situations the surgeon needs to re-baseline the device on a different part of

the specimen and repeat the measurement.

In Phase-2 of this study, ten surgeons used the CE device in real time in a series of 63 patients

and if the device suggested margin involvement then the protocol was to re-excise that margin.

The re-excision rate based on specimen radiography alone in the 63 patients was 37%. In 9

patients of these 63 the surgeon did not use the device according to protocol. In the remaining 54

patients the CE device reduced the re-excision rate to 17%. The high rate of re-excision in the 63

patients in Phase-2 reflects the population studied that included patients with both invasive

cancer with DCIS, some with DCIS alone and a number with invasive lobular cancers, many of

12

which were large. The sensitivity of the device was high and similar to that in Phase-1 with an

acceptable false positive rate of 23%. In the 54 patients where the device was used appropriately,

there were a further 5 patients with involved margins on pathology where the surgeon had not

baselined the device on normal breast tissue so all the margins were imaged as uniformly red or

green in colour. Surgeons involved in this study had relatively limited training with the device

and some surgeons had done less than 5 cases when using the device in real time. In the 49

patients in Phase-2 where the device was used and baselined appropriately the rate of re-excision

was only 8%. The present study is the first intra-operative use of this device by surgeons so it is

not surprising that user issues were identified. These have been remedied and the device

modified. The device was nonetheless easy for surgeons to use and the imaging of all margins

took less than 5 minutes with each margin taking only a few seconds.

The present study has confirmed high re-excision rates after BCS. There is a clear unmet need

for an easy to use intraoperative device to decrease re-excision rates in breast conserving

surgery. The CE device has the potential to reduce re‐excision rate by more than 50%. When

used in the current study its user interface software was still being developed and changes to the

device after the current study should improve its ease of use and increase its accuracy. Based on

the results we have obtained in this study it has the potential to reduce re-excision rates

significantly. Further studies of this device are eagerly awaited.

13

ROLE OF FUNDING SOURCE

This study was supported by an Educational Grant from LS Biopath who manufacture the

ClearEdge™ device. This study was performed and analysed independently. Support in use of

the device was provided by theatre staff in the Edinburgh Breast Unit who were trained in

troubleshooting the CE device.

Tables and Figures

Table 1a: Clinical and pathological features of patients and cancers in Phase-1

Table 1b: Clinical and pathological features of patients and cancers in Phase-2

Table 2a: Summary of the accuracy results using CE and X-ray imaging using 334 margins with CE device and 351 margins with the X-Ray in a total of 58 patients.

Table 2b: Summary of the accuracy results in Phase-2 using CE and X-ray imaging using 335 margins with CE device and 338 margins with the X-Ray in a total of

63 patients.

Table 3: Comparison of the re-operation rate achieved by using only X-Ray images to that potentially achieved based on reading the CE images.

Figure 1: CE device (left) and disposable head (right)

Figure 2: CE color coded image display

14

References

1. Siegel R, Naishadham D, Jemal A. Cancer Statistics, 2012. CA Cancer J Clin. 2012;62(1):10-29. PMCID: 22237781

2. Lee MC, Rogers K, Griffith K, et al. Determinants of Breast Conservation Rates: Reasons for Mastectomy at a Comprehensive Cancer Center. Breast J. 2009;15(1):34-40. PMCID: 19141132

3. Morrow M, Jagsi R, Alderman AK, et al. Surgeon Recommendations and Receipt of Mastectomy for Treatment of Breast Cancer. JAMA. 2009;302(14):1551-6. PMCID: 19826024

4. Elkhuizen PHM, van Slooten HJ, van de Velde CJH, et al. Local recurrence (LR) after breast-conserving therapy (BCT) in node-negative premenopausal patients: Influence of perioperative chemotherapy (PeCT). Eur J Cancer. 1998;34(Suppl 5):S101. PMCID:10694560

5. Kunos C, Latson L, Overmoyer B, et al. Breast conservation surgery achieving >= 2 mm tumor-free margins results in decreased local-regional recurrence rates. Breast J. 2006;12(1):28-36. PMCID:16409584

6. Clarke M, Collins R, Darby S, et al. Effects of radiotherapy and of differences in the extent of surgery for early breast cancer on local recurrence and 15-year survival: an overview of the randomised trials. Lancet. 2005;366(9503):2087-106. PMCID:16360786.

7. Houssami N, Macaskill P, Marinovich ML, et al. The association of surgical margins and local recurrence in women with early-stage invasive breast cancer treated with breast-conserving therapy: a meta-analysis. Ann Surg Oncol. 2014:21(3):717-30. PMCID: 24473640.

8. Balch GC, Mithani SK, Simpson JF, et al. Accuracy of intraoperative gross examination of surgical margin status in women undergoing partial mastectomy for breast malignancy. Am Surg. 2005;71(1):22-7. PMCID:15757052

9. Dillon MF, Mc Dermott EW, O'Doherty A, et al. Factors affecting successful breast conservation for ductal carcinoma in situ. Ann Surgical Oncol. 2007;14(5):1618-28. PMCID:17443388

15

10. Huston TL, Pigalarga R, Osborne MP, et al. The influence of additional surgical margins on the total specimen volume excised and the reoperative rate after breast-conserving surgery. Am J Surg. 2006;192(4):509-12. PMCID:16978962

11. Jacobs L. Positive margins: The challenge continues for breast surgeons. Ann Surg Oncol. 2008;15(5):1271-2. PMCID:18320287

12. Kotwall C, Ranson M, Stiles A, et al. Relationship between initial margin status for invasive breast cancer and residual carcinoma after re-excision. Am Surg. 2007;73(4):337-43. PMCID:17439024

13. Mendez JE, Lamorte WW, de las Morenas A, et al. Influence of breast cancer margin assessment method on the rates of positive margins and residual carcinoma. Am J Surg. 2006;192(4):538-40. PMCID:16978970

14. Olson TP, Harter J, Munoz A, et al. Frozen section analysis for intraoperative margin assessment during breast-conserving surgery results in low rates of re-excision and local recurrence. Ann Surg Oncol. 2007;14(10):2953-60. PMCID:17674109

15. Nedelman R, Dixon JM. Marking of excision specimens in patients undergoing stereotactic wide local excision for breast cancer. Br J Surg. 1992;79(1):55.

16. Singletary SE. Surgical margins in patients with early-stage breast cancer treated with breast conservation therapy. Am J Surg. 2002;184(5):383-93. PMCID:12433599

17. Allweis TM, Kaufman Z, Lelcuk S, et al. A prospective, randomized, controlled,multicenter study of a real-time, intraoperative probe for positive margin detection in breast-conserving surgery. Am J Surg. 2008;196(4):483-9. PMCID:18809049

18. Moran MS, Schnitt SJ, Giuliano AE, et al. Society of Surgical Oncology–American Society for Radiation Oncology Consensus Guideline on Margins for Breast-Conserving Surgery With Whole-Breast Irradiation in Stages I and II Invasive Breast Cancer. Ann Surg Oncol 2014 21(3):704-16.

19. Houssami N, Macaskill P, Marinovich ML, et al. Meta-analysis of the impact of surgical margins on local recurrence in women with early-stage invasive breast cancer treated with breast-conserving therapy. Eur J Cancer 2010 46(18):3219-32.

20. Meijnen P, Oldenburg HS, Peterse JL, et al.: Clinical outcome after selective treatment of patients diagnosed with ductal carcinoma in situ of the breast. Ann Surg Oncol 2008;15:235–243.

16

21. Dillon MF, Maguire AA, McDermott EW, et al.: Needle core biopsy characteristics identify patients at risk of compromised margins in breast conservation surgery. Mod Pathol 2008;21:39–45.

22. Ikeda T, Akiyama F, Hiraoka M, et al.: Surgical margin status as a cause of local failure after breast conserving therapy. Breast Cancer 1999;6:93–97.

23. Chagpar AB, Martin RC II, Hagendoorn LJ, et al.: Lumpectomy margins are affected by tumor size and histologic subtype but not by biopsy technique. Am J Surg 2004;188:399–402.

24. Kurniawan ED, Wong MH, Windle I, et al.: Predictors of surgical margin status in breast‐conserving surgery within a breast screening program. Ann Surg Oncol 2008;15:2542–9.

25. McCahill LE, Single RM, Aiello Bowles EJ, et al.: Variability in reexcision following breast conservation surgery. JAMA 2012;307:467–75.

26. Jeevan R, Cromwell DA, Trivella M, et al.: Reoperation rates after breast conserving surgery for breast cancer among women in England: Retrospective study of hospital episode statistics. BMJ 2012;345:e4505.

27. D’Halluin F, Tas P, Rouquette S, et al.: Intra‐operative touch preparation cytology following lumpectomy for breast cancer: A series of 400 procedures. Breast 2009;18:248–53.

28. Klimberg VS, Harms S, Korourian S: Assessing margin status. Surg Oncol 1999;8:77–84.

29. Sevick‐Muraca EM: Translation of near‐infrared fluorescence imaging technologies: Emerging clinical applications. Annu Rev Med 2012;63:217–31.

30. Pani S, Cook EJ, Horrocks JA, et al.: Characterization of breast tissue using energy‐dispersive X‐ray diffraction computed tomography. Appl Radiat Isot 2010;68:1980–7.

31. Doyle TE, Factor RE, Ellefson CL, et al.: High‐frequency ultrasound for intraoperative margin assessments in breast conservation surgery: A feasibility study. BMC Cancer 2011;11:444.

32. Tang R, Buckley JM, Fernandez L, et al.: Micro‐computed tomography (micro‐CT): A novel approach for intraoperative breast cancer specimen imaging. Breast Cancer Res Treat 2013;139:311–6.

33. Thill M: MarginProbe1: Intraoperative margin assessment during beast conserving surgery by using radiofrequency spectroscopy. Expert Rev Med Devices 2013;10:301–15.

17

34. Keller MD, Majumder SK, Mahadevan‐Lansen A: Spatially offset Raman spectroscopy of layered soft tissues. Optics Letters 2009;34:926–8.

35. Haka AS, Volynskaya Z, Gardecki JA, et al.: Diagnosing breast cancer using Raman spectroscopy: Prospective analysis. J Biomed Opt 2009;14:054023.

36. Wilke LG, Brown JQ, Bydlon TM, et al.: Rapid noninvasive optical imaging of tissue composition in breast tumor margins. Am J Surg 2009;198:566–74.

37. Mamou J, Oelze ML, O’Brien WD Jr, et al.: Extended threedimensional impedance map methods for identifying ultrasonic scattering sites. J Acoust Soc Am 2008;123:1195–208.

38. Thill M, Baumann K: New technologies in breast cancer surgery. Breast Care (Basel) 2012;7:370–6.

39. Pappo I, Spector R, Schindel A, et al.: Diagnostic performance of a novel device for real‐time margin assessment in lumpectomy specimens. J Surg Res 2009;160:277–81.

40. Schnabel F, Tafra L, The MarginProbe Study group: A randomized, prospective multicenter study of the impact of intraoperative margin assessment with adjunctive use of MarginProbe vs. standard of care. 34th Annual San Antonio Breast Cancer Symposium, 2011; San Antonio, TX, USA.

41. Thill M, Dittmer C, Baumann K, et al.: MarginProbe(1)—Final results of the German post‐market study in breast conserving surgery of ductal carcinoma in situ. Breast 2014;23:94–6.

42. Dixon JM, Newlands C, Dodds, C, et al.: Under Estimation of Tumour Size by Imaging is a Major Factor Associated with Incomplete Excision in Women Undergoing Breast Conserving Surgery for Invasive Breast Cancer. Br J Surg 2016 (In Press)

18