MRI techniques for prediction of local tumor progression after high-intensity focused ultrasonic ablation of prostate cancer

OBJECTIVE. The purpose of this study was to evaluate the diagnostic performance of dynamic contrast-enhanced MRI (DCE-MRI) and of T2-weighted MRI with diffusion-weighted imaging (DWI) for predicting local tumor progression after high-intensity focused ultrasonic ablation of localized prostate cancer. MATERIALS AND METHODS. Twenty-seven patients who had increased levels of prostate-specific antigen after high-intensity focused ultrasonic ablation underwent MRI and endorectal biopsy. The MR images and biopsy results were correlated for six prostate sectors. Residual or recurrent prostate cancer after treatment was defined as local tumor progression if the biopsy results showed cancer foci. Two readers blinded to the clinical findings and biopsy results used a 5-point scale to independently assess DCE-MR images and T2-weighted and diffusion-weighted MR images. The results were compared by use of the McNemar test with Bonferroni correction, generalized estimating equations, and receiver operating characteristic analysis. RESULTS. After high-intensity focused ultrasonic ablation, local tumor progression was pathologically detected in 54 (33%) of 162 sectors in 18 patients. The sensitivities of DCE-MRI and T2-weighted MRI with DWI were 80% and 63% for reader 1 (p=0.004) and 87% and 70% for reader 2 (p=0.004). The specificities of DCE-MRI and T2-weighted MRI with DWI were 68% and 78% for reader 1 (p=0.002) and 63% and 74% for reader 2 ( p < 0.001). The accuracy rates of DCE-MRI and T2-weighted MRI with DWI were 72% and 73% for reader 1 ( p > 0.05) and 71% and 73% for reader 2 ( p > 0.05). The areas under the receiver operating characteristic curve for DCE-MRI and T2-weighted MRI with DWI were 0.77 and 0.77 for reader 1 and 0.85 and 0.81 for reader 2. CONCLUSION. For prediction of local tumor progression of prostate cancer after high-intensity focused ultrasonic ablation, DCE-MRI was more sensitive than T2-weighted MRI with DWI, but T2-weighted MRI with DWI was more specific than DCE-MRI.