Date of Award

January 2023

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Jonathan Langdon

Second Advisor

Leslie Scoutt

Abstract

In the United States, breast cancer is one of the most diagnosed cancers in women. Early detection, often via mammography, and intervention have been shown to reduce mortality. However, not all cancers are mammographically evident in early stages, if at all. As a result, ultrasound has been increasingly used to supplement mammography for breast cancer detection and assessment, particularly in dense breasts. Recent advancements in ultrasonography include the ability to characterize the stiffness of biological tissues. Shear Wave Elastography (SWE) is one such development used to quantify tissue stiffness within a region of interest.

The resistance of soft tissue to deformation depends on the molecular makeup of the tissue components as well as elements of tissue structure, such as stromal and connective tissue. As tumor growth often involves architectural changes that cause increased stiffness compared to normal neighboring tissue, SWE has the potential to compliment mammography and B-mode ultrasound for breast lesion characterization. Studies establishing the clinical value of SWE may aid in its incorporation into diagnostic guidelines.

This study aimed to quantify the performance of 2D SWE for differentiating benign and malignant breast lesions in women with abnormal mammography via a systematic review of the literature and meta-analysis. A systematic search of PubMed, Scopus, Embase, Ovid-Medline, Cochrane Library and Web of Science was performed. Studies of diagnostic accuracy published prior to June 2021 using SWE to evaluate abnormal breast tissue with at least 50 lesions that reported quantitative shear wave speed (SWS) parameters (the mean (SWSmean), maximum (SWSmax), minimum (SWSmin), or standard deviation (SWSSD) of the SWS) and thresholds and included a reference standard of either biopsy or 2-year stability were included in the analysis. The QUADAS- 2 tool was used to assess possible bias within studies as well as their applicability.

87 studies of diagnostic accuracy were included, encompassing 17,810 women (47) with 19,043 lesions (7,623 malignant). A hierarchical summary receiver operating characteristic model produced the following summary sensitivities and specificities: 0.86 [0.83, 0.88] / 0.87 [0.84, 0.88] for SWSmean, 0.83 [0.80, 0.85]/ 0.88 [0.86, 0.90] for SWSmax, 0.86 [0.74, 0.93]/ 0.81 [0.69, 0.89] for SWSmin, and 0.82 [0.77, 0.86] / 0.88 [0.85, 0.91] for SWSSD, respectively. By calculating and utilizing the resulting likelihood ratios, SWE was shown capable of downgrading BI-RADS 4a and upgrading BI-RADS 3 lesions. Thus, SWE has the potential to provide increased discriminative power in the diagnosis of breast cancer if used synergistically with mammography and B-mode ultrasound.

Current society guidelines do not provide definitive recommendations about the role of SWE in screening and diagnosis, nor its counterpart strain elastography (SE). The literature suggests that a combination of SE and SWE may provide better discriminatory power than SWE alone and serve as an adjunct to current diagnostic techniques, opening an avenue for future study.

Comments

This is an Open Access Thesis.

Open Access

This Article is Open Access

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