Follow-up after focal therapy of the prostate with high intensity focused ultrasound (HIFU) using contrast enhanced ultrasound (CEUS) in combination with MRI image fusion

INTRODUCTION: Focal therapy (FT) of the prostate for low risk prostate cancer (PCa) is an alternative to traditional definite treatment options like external beam radiotherapy or radical prostatectomy. However, follow up after FT is still challenging and is subject to current studies. Significance of imaging after FT such as multiparametric MRI (mpMRI) is currently not well established. In this study, we aimed to evaluate the efficacy of alternative imaging during the follow up of low risk PCa treated with focal HIFU therapy using CEUS and image fusion. MATERIALS AND METHODS: Retrospective single arm study in patients with uni- or bilateral, low or intermediate risk prostate cancer treated with HIFU at our institution between October 2016 and January 2018. CEUS in combination with image fusion using an axial T2-weighted MRI sequence was performed during follow up 3, 6, 9 and 12 months after the therapy. RESULTS: 4 consecutive patients with Gleason score (GS) 6 and 4 patients with GS 7a prostate cancer were included in the study. Hemiablation was performed in 7 patients with unilateral tumor. One patient underwent whole gland treatment due to histological proven bilateral PCa. Mean patient age at time of therapy was 70.3 (54-83) years and mean Prostate-specific antigen (PSA) level prior treatment was 7.8 ng/ml (2.1-14.4), after 3 months mean PSA level was 3.9 ng/ml (0.1-7.2), after 6 months 3.5 ng/ml (0.2-6.0), after 9 months 3.1 ng/ml (0.2-6.8) and 3.3 ng/ml (0.2-6.1) after 12 months. CEUS showed no signs of microvascularisation after 3, 6, 9 and 12 months in the ablated zone. 3 months posttreatment the necrotic tissue was still visible in the B-mode scan, although with no signs of vascularization performing CEUS. After 6 months the ablated side of the prostate was almost completely atrophic. And after 9 months the necrotic tissue was completely resolved. Between 9 and 12 months no changes in microvascularisation and perfusion could be shown. CONCLUSIONS: MpMRI/CEUS image fusion is a cost-effective and feasible technique to monitor the perfusion of the ablation zone after focal therapy of the prostate.