Imaging Plus Elastography Enhances Surgical Margin Assessment in Breast Cancer

Brendan Kennedy, PhD

Brendan Kennedy, PhD

Quantitative microelastography demonstrated increased sensitivity, specificity, and accuracy in detecting positive surgical margins in combination with optimal coherence tomography versus optimal coherence tomography alone in women who received breast-conserving surgery, according to findings from a study published in Cancer Research.^1,2

The combined imaging modality approach demonstrated 92.9% sensitivity, 96.4% specificity, and 95.8% accuracy rates in detecting cancer within 1 mm of excised surgical margins compared with optimal coherence tomography imaging alone, which demonstrated 69.0% sensitivity, 79.0% specificity, and 77.5% accuracy rates.

“Imaging the microscale stiffness of tissue using quantitative microelastography has the potential to reduce reexcision rates in breast-conserving surgery. Further, by quantifying tissue stiffness, we remove the subjectivity that is inherent to the surgeon’s sense of touch,” study coauthor, Brendan Kennedy, PhD, associate professor in the School of Engineering at The University of Western Australia, stated in a press release.

Although x-rays are commonly used intraoperatively to detect residual disease in surgical margins, the imaging tool can’t detect microscopic traces of disease, study coauthor, Christobel Saunders, MBBS, professor in the School of Medicine at The University of Western Australia, also stated in the press release.

“Despite living in the digital age, surgeons must routinely rely on their eyesight and sense of touch to determine if they have removed the entire tumor during breast-conserving surgery,” said Kennedy in the press release. “Due to lack of adequate tools, 20% to 30%of patients must return for additional surgery, resulting in substantial physical and financial burdens and increased risk of complications.”

In order to define a more robust detection strategy, investigators evaluated the diagnostic accuracy of using quantitative microelastography in conjunction with optical coherence tomography versus optical coherence tomography alone to detect residual cancer in the margins of breast-conserving surgical specimens.

Investigators enrolled 90 patients with plans to undergo breast cancer surgery. Of these patients, 83 received breast-conserving surgery, and 7 received mastectomy. After surgery, quantitative microelastography and optimal coherence tomography analyses were performed on the resection margins of the specimens. The specimens were also submitted for standard histopathological assessment.

Three-dimensional regions of interest were selected from patients’ scans to allow for a comparison between the imaging analyses and histopathological assessment. At least 1 region of interest was chosen for every surgical margin that was sampled in the study. The region of interest was considered positive for cancer if the pathologist found traces of disease within 1 mm of the margin and histological section.

Prior to employing quantitative microelastography and optimal coherence tomography, investigators trained 2 surgeons, 2 engineers, 1 medical sonographer, 1 pathology assistant, and 1 medical resident to determine the accuracy of the technology in detecting positive surgical margins among all mastectomy and several breast-conserving specimens (n = 12).

The remaining specimens from 71 patients who received breast-conserving surgery were tested for residual disease within 1 mm of the surgical margins with quantitative microelastography and optimal coherence tomography compared with standard postoperative histological assessment.

A total 174 regions of interest were selected and evaluated for histology, 154 of which were included in the reader assessment. The most common reasons for exclusion included thermal damage, according to postoperative histology (n = 3); inconclusive registration with histology sections (n = 4), insufficient contact between the specimen, silicone layer, and the imaging window (n = 3); imaging artifacts (n = 4); inadequate elasticity data plated on solid tissue (n = 2); inadequate data to make a definitive conclusion (n = 2); and a region size of less than 1 mm (n = 2).

Of the 154 regions of interest, 24 had cancer within 1 mm of the surface, which translated to a 15.6% prevalence rate. The majority of tissue types that were reflected in the analysis included adipose tissue, stromal tissue, and parenchymal tissue.

“The ideal scenario would be to perform the imaging in the surgical cavity immediately after the specimen has been removed,” Kennedy concluded in the press release. “This would give surgeons a direct indication of whether any tumor had been missed. As such, our next goal is to develop a handheld quantitative microelastography probe to enable intraoperative imaging.”

References

1. Kennedy KM, Zilkens R, Allen WM, et al. Diagnostic accuracy of quantitative micro-elastography for margin assessment in breast-conserving surgery. Cancer Res. 2020;80(8):1773-1783. doi: 10.1158/0008-5472.CAN-19-1240.
2. High-resolution imaging coupled with elastography may accurately detect breast cancer in surgical margins [news release]: AACR; Published April 15, 2020. https://bit.ly/35dIiAe. Accessed April 28, 2020.