Equivalent cross-relaxation rate imaging and diffusion weighted imaging for early prediction of response to bevacizumab-containing treatment in colorectal liver metastases—preliminary study

Abstract

PurposeTo evaluate and compare the usefulness of equivalent cross-relaxation rate (ECR) imaging (ECRI) and diffusion-weighted imaging (DWI) in the early prediction of the response of bevacizumab-containing treatments of colorectal liver metastases. Methods and materialSeven patients received bevacizumab-containing treatments for colorectal liver metastases. Serial magnetic resonance imaging was performed to evaluate responses before and 2 weeks after starting chemotherapy. In the ECRI, we adopted the off-resonance technique for preferential saturation of immobile protons to evaluate the ECR values. A single saturation transfer pulse frequency was used at a frequency of 3.5 ppm downfield from the water resonance. In the DWI, the apparent diffusion coefficient (ADC) value commonly used with two b-values was acquired by using diffusion weightings of 0 and 800 s/mm2. The region of interest of the metastatic lesions in the liver was separately measured by ECRI and DWI. Tumor response was assessed by response evaluation criteria in solid tumors criteria 8 weeks after starting chemotherapy. ResultsIn this study, we had four responders and three nonresponders. There was a significant difference in the pretreatment ECR values between the responders and nonresponders (P=.01); there was no significant difference in the ADC values between the two groups. Analysis of the percentage difference between the pretreatment and post-treatment values, termed as percentage change, showed that there were no significant differences in the percentage change of the ADC values between both groups; however, the percentage change in the ECR value was significantly greater for the responders than for the nonresponders (−41.6%±17.1% vs. –12.9%±6.9%, respectively; P=.04). ConclusionThe pretreatment ECR value and percentage change of the ECR value 2 weeks after starting chemotherapy were useful parameters in the early prediction of response to bevacizumab-containing treatment in colorectal liver metastases.