Diagnostic Accuracy of Quantitative Micro-Elastography for Margin Assessment in Breast-Conserving Surgery

Abstract

Inadequate margins in breast-conserving surgery (BCS) are associated with an increased likelihood of local recurrence of breast cancer. Currently, approximately 20% of BCS patients require repeat surgery due to inadequate margins at the initial operation. Implementation of an accurate, intraoperative margin assessment tool may reduce this re-excision rate. This study determined, for the first time, the diagnostic accuracy of quantitative micro-elastography (QME), an optical coherence tomography (OCT)-based elastography technique that produces images of tissue microscale elasticity, for detecting tumor within 1 mm of the margins of BCS specimens. Simultaneous OCT and QME were performed on the margins of intact, freshly excised specimens from 83 patients undergoing BCS and on dissected specimens from 7 patients undergoing mastectomy. The resulting three-dimensional images (45 Â 45 Â 1 mm) were coregistered with postoperative histology to determine tissue types present in each scan. Data from 12 BCS patients and the 7 mastectomy patients served to build a set of images for reader training. One hundred and fifty-four subimages (10 Â 10 Â 1 mm) from the remaining 71 BCS patients were included in a blinded reader study, which resulted in 69.0% sensitivity and 79.0% specificity using OCT images, versus 92.9% sensitivity and 96.4% specificity using elasticity images. The quantitative nature of QME also facilitated development of an automated reader, which resulted in 100.0% sensitivity and 97.7% specificity. These results demonstrate high accuracy of QME for detecting tumor within 1 mm of the margin and the potential for this technique to improve outcomes in BCS.Significance: An optical imaging technology probes breast tissue elasticity to provide accurate assessment of tumor margin involvement in breast-conserving surgery.

Handheld volumetric manual compression‐based quantitative microelastography

“…In Figure F, representative regions of fibrous tissue and adipose tissue are selected by the black and red dashed frames, with the measured elasticity value of 53.8 ± 16.7 kPa and 12.6 ± 7.4 kPa, respectively. The fibrous tissue presents higher elasticity than the surrounding adipose tissue, yet relatively low when compared to the elasticity in the tumor regions in Figures F and F, as expected from previous QME studies . The measured elasticity values of IDC, DCIS and benign tissues shown in our results are also consistent with previous study using an OCT‐elastography‐based optical biopsy technique .…”

“…Following the scans, each mastectomy tissue sample was bisected and placed in two cassettes to enable preparation for histology in the same plane as the en face plane of the QME scans. For WLE specimens, the histology was prepared following the standard histological procedure used at Fiona Stanley Hospital, where each specimen was sliced in a “bread‐loaf” fashion from the lateral to medial margin, in the same plane as OCT/QME B‐scans . The histology was acquired ~1 week after the scan of each specimen.…”

“…QME has recently been demonstrated in a number of applications . Our group has primarily focused on developing QME for tumor margin assessment in BCS . Based on the premise that tumors are often stiffer than surrounding benign tissues in breast , providing surgeons with an intraoperative map of elasticity could help to reduce high re‐excision rates (currently 20‐30% ).…”

“…Based on the premise that tumors are often stiffer than surrounding benign tissues in breast , providing surgeons with an intraoperative map of elasticity could help to reduce high re‐excision rates (currently 20‐30% ). To date, QME has been primarily implemented in bulky benchtop setups , limiting its compatibility with clinical deployment. To overcome this limitation, we have recently developed a prototype handheld QME probe which holds promise for intraoperative use .…”

Camera-based optical palpation

“…The most widely developed approach is optical coherence elastography (OCE) 2 , 3 , 16 – 19 which combines optical coherence tomography (OCT) and a loading mechanism, typically either a quasi-static compression or an acoustic excitation, to measure the local mechanical response of tissue from which a map of elasticity is derived. OCE has an attractive combination of features, including rapid acquisition, micrometre-scale resolution and millimetre to centimetre field-of-view 20 , 21 , and has been proposed for a number of applications including tumour margin assessment and keratoconus detection 22 – 26 . Brillouin microscopy is another prominent technique which utilises confocal microscopy to measure the Brillouin frequency shift induced by vibrations of phonons in the tissue.…”