ARFI, VisR and DDAI Ultrasound for Improving Discrimination of Malignant and Unresponsive Breast Cancer

The primary objective of breast cancer screening is to identify early stage cancer, or precancerous lesions, at a time before symptoms emerge and when treatment is likely to result in a cure. Screening is beneficial when it averts progression of disease to metastasis and/or death, but adverse effects to patients (and unnecessary medical expense) may result downstream from false positives and indiscrimination of masses that will not respond to treatment. The sensitivity of digital mammography, the current screening standard in the US, has been reported in the range of 0.40 to 0.85, with a positive predictive value of 0.31. Sensitivity is increased by augmenting mammography with MRI and B-Mode ultrasound, but false positive rates may also increase3. There exists a vital need for a screening technology that exhibits high sensitivity and specificity for cancer detection with early identification of unresponsive masses.

This urgent need could be met by exploiting new imaging biomarkers. Specifically, the mechanical properties of breast tissue have been used for cancer detection, with both elasticity and viscosity demonstrated for discriminating malignant from benign lesions. Further, tissue anisotropy has been shown to correlate with core biopsy result and tumor grade, with large cancers significantly more anisotropic than small cancers. Importantly, while both MRI and ultrasound can be used to measure these biomarkers, ultrasound's cost effectiveness and ease of implementation render it an efficient platform to pursue.

The long-term goal of this research program is to develop a new ultrasound-based breast-screening tool to augment mammography. As a critical first step toward achieving this goal, the primary objective of the proposed research is to evaluate in vivo the diagnostic relevance of ultrasound-derived metrics for stiffness, elasticity, viscosity, and anisotropy. These biomarkers will be measured using novel, noninvasive ultrasound technologies under development in Dr. Gallippi's laboratory: 1) Acoustic Radiation Force Impulse (ARFI) ultrasound for interrogating tissue stiffness, 2) Viscoelastic Response (VisR) ultrasound for assessing tissue elasticity and viscosity, and 3) Dynamic Displacement Anisotropy Imaging (DDAI) for measuring tissue anisotropy. These technologies have been demonstrated previously for delineating atherosclerosis, muscular dystrophy, and renal dysfunction.

A.1.2.State the research question(s) (i.e., specific study aims and/or hypotheses).

The investigators hypothesize that ultrasound-derived stiffness, elasticity, viscosity, and anisotropy will correlate with lesion malignancy and response to treatment. To test this hypothesis, they will pursue the following specific aims:

Aim #1: Quantify the ability of ultrasound-derived stiffness, elasticity, viscosity, and anisotropy to detect malignancy. ARFI, VisR, and DDAI imaging will be performed on suspicious breast lesions in 40 women with BIRADS-4a, 4b, 4c, or -5 ratings. The diagnostic accuracy of imaging metrics will analyzed, with malignancy confirmed by histology as the outcome.

Aim #2: Quantify the ability of ultrasound-derived stiffness, elasticity, viscosity, and anisotropy to predict a positive response to treatment. ARFI, VisR, and DDAI imaging will be performed serially - once every four weeks over the course of neoadjuvant chemotherapy (NAC) - on malignant breast lesions in 40 women. Changes in outcome metrics over time will be correlated to overall reduction in tumor size (diameter and area). The ability of ultrasound metrics to predict a positive response to treatment will be examined. A positive response to treatment will be determined according to the Response Evaluation Criteria in Solid Tumors (RECIST) guidelines.