Shear-wave elastography in detection of residual breast cancer after neoadjuvant chemotherapy.

Abstract

102 Background: To evaluate the accuracy of shear-wave elastography (SWE) in detecting residual cancer after neoadjuvant chemotherapy. Methods: This retrospective study was approved by our institutional review board and the requirement for written informed consent was waived. From January 2012 to February 2013, 71 women with stage II-III invasive breast cancers who received neoadjuvant chemotherapy and were imaged with B-mode ultrasonography (US), SWE, and magnetic resonance (MR) imaging before surgery were included. Presence of residual cancer was evaluated and categorized according to the morphology on preoperative B-mode US and MR imaging. Quantitative elasticity values (maximum kPa) were acquired for primary lesions depicted on US. Pathological complete response (pCR) was defined as no residual invasive cancer cells. The quantitative SWE values were compared between the pCR and non-pCR group using independent samples t-test. The areas under the receiver operating characteristics curve (AUC), sensitivities, and specificities of B-mode US, MR, and SWE for detecting residual cancer were compared, with histopathologic examination as the reference standard. Results: Of the 71 women, 15 (21%) achieved pCR. The mean size of residual invasive cancers was 2.2 cm (range 0.1-6.4 cm).The maximum SWE value was significantly higher in the non-pCR group (mean, 122.9 kPa) than in the pCR group (30.6 kPa) (P < 0.001). The AUC of SWE for detecting residual cancer (0.893) was higher than that of B-mode US (0.684) (P = 0.001) and comparable to that of MR (0.884) (P = 0.825). The optimal cut-off value, yielding the maximal sum of sensitivity and specificity, was 98.1 kPa, and the sensitivity and specificity of SWE at that cut-off value were 66% (37 of 56) and 100% (15 of 15). When SWE was added to B-mode US, the AUC value was significantly increased to 0.830 (P = 0.039). Conclusions: SWE was accurate in the detection of residual cancer after neoadjuvant chemotherapy. When SWE was combined with B-mode US, the accuracy was significantly improved.