Contrast-Enhanced Ultrasonography in Evaluation of the Therapeutic Effect of Chemotherapy for Patients with Liver Metastases

BACKGROUND The therapeutic effect of chemotherapy for liver metastases is currently determined by changes in tumor diameter depicted on computed tomography (CT) and magnetic resonance imaging, but it cannot accurately determine if there is central necrosis. Furthermore, due to the risk of radiation exposure and high cost, frequent examination using these methods places a heavy burden on patients. Meanwhile, real-time observation of blood flow and vessel morphology within tumors has become possible by contrast-enhanced ultrasonography (CEUS). However, use of CEUS in evaluating the therapeutic effect of anticancer chemotherapy has rarely been investigated. This study investigated whether changes in the time-intensity curve (TIC) of CEUS are useful indicators of the therapeutic effect of chemotherapy. METHODS Five patients with liver metastases who had undergone CEUS before and after chemotherapy were included in this study. The TIC of each time point was prepared to examine whether the following five TIC parameters serve as indicators of the therapeutic effect of chemotherapy: peak intensity, time to wash-in, time to peak intensity, slope of wash-in, and area under the curve. In each parameter, rate of change (ROC) was calculated by the expression [(values before chemotherapy minus those after chemotherapy)/those before chemotherapy × 100(%)]. RESULTS (i) Among the five TIC parameters tested, ROC of the slope of wash-in and the area under the curve reflected the therapeutic effect of chemotherapy better than the remaining three parameters. (ii) TIC parameters after one cycle of chemotherapy were examined in two of five patients, and changes in the slope of wash-in and the area under the curve were in good agreement with the computed tomography findings indicative of the therapeutic effect after the fourth chemotherapy cycle. CONCLUSION The findings of this study suggest that ROC of the slope of wash-in and the area under the curve of the TIC are useful in evaluating the therapeutic effect of chemotherapy. Furthermore, there is a possibility that TIC analysis may enable early prediction of the therapeutic effect.