Shear Wave Elastography: Is It a Valuable Additive Method to Conventional Ultrasound for the Diagnosis of Small (≤2 cm) Breast Cancer?

The aim of this study is to evaluate the diagnostic value of shear wave elastography (SWE) added to conventional ultrasound (US) in the diagnosis of small (≤2 cm) breast cancer. Among 410 patients who underwent SWE before US-guided biopsy from June 2012 to June 2013, 171 patients (mean age: 45.17 ± 9.37 years) with 177 small (≤2 cm) breast lesions were enrolled in this study. Diagnostic performances of each quantitative SWE parameters were calculated by receiver operating characteristic (ROC) curves. Performances of conventional US and US combined to SWE was also compared. Histologic diagnosis was used as a reference standard. Of the 177 lesions, 22 lesions (12.4%) were malignant and 155 (87.6%) were benign. With respect to conventional US, when a cutoff point between category 3 and 4a was used, the A(z) value was 0.915 (100% sensitivity, 36.8% specificity, 18.3% positive predictive value (PPV), and 100% negative predictive value (NPV)). All average quantitative elastography values were significantly higher in malignant lesions compared to benign lesions (P = 0.001). The E(max) value with a cutoff of 87.5 kPa had the highest A(z) value of 0.796 (68.2% sensitivity and 87.1% specificity, 42.9% PPV, and 95.1% NPV). A(z) value of combined data (0.861, 95% CI: 0.801, 0.909) was significantly lower than that of conventional US alone (P = 0.02). By using an E(max) value for downgrading Breast Imaging Reporting and Data System (BI-RADS) category 4a lesions to category 3, 76/94 category 4a lesions (80.9%) were downgraded. After downgrading, 5 cancers were missed and the malignancy rate of category 3 lesions increased from 0% (0/55) to 3.8% (5/133) (P = 0.01). In conclusion, combined use of SWE and conventional US increased the specificity by reducing the number of unnecessary biopsies in differential diagnosis of small breast lesions. However, we propose that the application of conservative strategy for downgrading of soft category 4a lesions would be appropriate to minimize false-negative cases.