The utility of intraoperative contrast-enhanced ultrasound in detecting residual disease after focal HIFU for localized prostate cancer.

Abstract Background and objectives Focal high intensity focused ultrasound (HIFU) is an emerging treatment for selected men with localized prostate cancer. A limitation of HIFU is the absence of a reliable tool to measure treatment effect intraoperatively. Contrast-enhanced ultrasound (CEUS) has been shown to be a promising modality for assessing the extent and boundaries of tissue ablation. The aim of this study was to assess the value of CEUS immediately after focal HIFU. Materials and methods Retrospective analysis of a prospectively maintained registry including consecutive men undergoing focal HIFU (Focal One). Candidates for focal HIFU were treatment naive men with ≥10 years life expectancy, prostate-specific antigen (PSA) ≤ 20 ng/ml, TNM primary tumor, regional lymph nodes, distant metastasis stage ≤ T2c N0 M0 with a multiparametric MRI (mpMRI) visible lesion concordant with histologically proven prostate cancer. CEUS evaluation was performed immediately at the end of the procedure. Based on the surgeon's estimation of CEUS imaging, re-HIFU was performed, followed by another CEUS evaluation. To test our hypothesis, the results of the CEUS were compared to the results of early mpMRI to rule out clinically significant cancer. The concordance between the 2 tests was measured using the Cohen's kappa. The best model including relevant predictors was calculated with CEUS or with mpMRI to determine their respective added value. Results Of 66 men who underwent HIFU, 32 met eligibility criteria. Bifocal treatment was performed in 1 man, increasing the number of treated lesions to 33. Further ablation based on CEUS was delivered intraoperatively to 13 lesions (39%). The positive biopsy rate for clinically significant cancer in the treated zones was 30% (10/33). The negative predictive value of CEUS and early mpMRI was 71% (95% confidence interval: 59%–82%). Concordance between CEUS and mpMRI was significant with a 72.7% agreement (P = 0.001). The model with CEUS showed the best accuracy with an area under the curve of 0.881. Conclusion CEUS has a higher added value compared to early mpMRI in ruling out clinically significant cancer after focal HIFU. It should be evaluated whether the use of CEUS intraoperatively enhances the efficacy of focal HIFU.