Comparative Study Between Shear and Strain Elastography in Monitoring the Response to NAC in Breast Cancer Patients

Breast cancer (BC) is one of the most common malignant tumors in global population, with the highest morbidity and mortality rates among female.(1) Neoadjuvant chemotherapy (NAC) has become an important supplement of comprehensive and precise treatment of BC. Neoadjuvant chemotherapy (NAC) is increasingly used to induce tumor shrinkage, thereby allowing smaller surgical resection, eliminating clinically silent micro metastases, and providing prognostic information based on the extent of pathologic response(.2-4) Pathological complete response (pCR) is increasingly seen after neoadjuvant chemotherapy (NACT) for invasive breast cancer. Confident identification of pCR may lead to less radical breast surgery and to sentinel node biopsy rather than axillary clearance in women with pre-treatment positive nodes.(5)Response to NACT is routinely assessed using magnetic resonance imaging (MRI), greyscale ultrasound (US), and mammography.(6) In some studies, MRI has been shown to be superior to US.(7-8) however, MRI has the disadvantages of being time-consuming, expensive, requiring intravenous contrast agent . Ultrasonic elastography (UE) has been widely used to qualitatively and quantitatively evaluate differences in lesion stiffness or elasticity. Currently, the two most frequently used UE techniques for examination of breast diseases are strain elastography (SE) and shear-wave elastography (SWE). In practice, UE is a complementary technique for differentiating benign from malignant breast masses (9,10). Breast cancers with more aggressive pathological properties tend to have higher stiffness values .Strain elastography (SE) may be predictive of response in the early stage of treatment with high sensitivity (SEN) and specificity (SPE).(11,12) Pretreatment tumor stiffness measured by shear wave elastography (SWE) has a significant relationship with the subsequent reduction in tumor cellularity.(13) In case of NACT, early evaluation of relative changes in tumor stiffness could effectively predict the response and might indicate better therapeutic strategies.(14)