Breast Elasticity Imaging During Neoadjuvant Chemotherapy

Neoadjuvant chemotherapy (NACT) is the standard of care for treatment of locally advanced breast cancer (LABC) and inflammatory breast cancer, and is recently being used in earlier stage breast cancer. The ideal outcome of NACT is pathological complete response (pCR), which itself has shown to be associated with improved disease-free survival. However, pCR is currently determined at the time of the surgery when the patient has received the whole cycle of the treatment. Early detection of non-responders to NACT could be used to halt ineffective treatment and start a new chemotherapeutic regimen in order to achieve better tumor response and overall survival. Current techniques to monitor response to NACT based on tumor size changes include mammography, physical examination, ultrasonography and MRI. Clinically assessing tumor size has been shown to be only moderately useful for chemotherapy response prediction in these patients because tumor shrinkage is a late marker of effective treatment. Metabolic activities and microstructure changes induced by NACT can be determined using functional imaging methods such as PET-CT, contrast enhanced MRI and diffuse optical spectroscopy. However, the application of these methods is limited due to high cost and intravenous injection of exogenous contrast agents. Limited studies have shown the potential of ultrasound elastography to be useful in predicting and monitoring response to NACT in breast cancer tumors based on tumor stiffness. Harmonic Motion Imaging (HMI) is a novel ultrasound elastography technique that applies an oscillatory force locally and at different depths in the tissue, in order to determine the characteristics of the resulting localized harmonic motion using high precision tracking methods. Highly localized harmonic motion can be noninvasively generated by ultrasonic beams deep inside the tissue and estimated at high precision, by using RF signals and cross-correlation methods. In addition to not being burdened by the drawbacks encountered by existing techniques, due to the highly localized and harmonic nature of the response, the motion characteristics can be directly linked to the local tissue stiffness. In this study, the investigators propose to compare the changes in the measurements provided by HMI and pathological response rate, between baseline, during treatment and end of the treatment to assess whether HMI can early predict the tumor response to neoadjuvant therapy.