Oncological Outcome and Value of Postoperative Magnetic Resonance Imaging after Focal High-Intensity Focused Ultrasound Therapy for Prostate Cancer.

Introduction: Focal therapy (FT) by high-intensity focused ultrasound (HIFU) is an emerging option for localized prostate cancer (PC). Due to the lack of long-term data, a close monitoring after FT is essential, but there are still uncertainties about the optimal follow-up regimen. Here we report on a series of FT-HIFU patients with the focus on oncological short-term outcome and the value of postoperative magnetic resonance imaging (MRI). Methods: We included 21 patients treated by FT-HIFU using the Focal One (R) device (EDAP TMS, France) between November 2015 and May 2018. PC localization was assessed by preoperative multiparametric MRI (mpMRI) and transrectal ultrasound-guided targeted and systematic biopsy. Oncological follow-up included prostate-specific antigen (PSA) development, mpMRI, control biopsies (targeted and systematic) of the treated and untreated areas and salvage treatment rate. Control mpMRI and control biopsy were performed after 6-12 months. Results: 15 patients (71.4%) were managed by focal ablation of a solitary lesion, while 6 patients (28.6%) underwent zonal tumor ablation. All patients underwent control mpMRI and biopsy. After a mean follow-up period of 11.7 months, cancer relapse was detected in 8 patients (38.1%), with 4 patients (19%) having infield recurrence. Postoperative mpMRI revealed 3 out of 4 infield PC relapses but missed 5 out of 7 outfield relapses. Clinically significant cancer recurrence was present in 1 patient (4.8%), which was missed by mpMRI. Posttreatment mpMRI had a sensitivity, specificity, positive and negative predictive value of 62.5, 92.3, 83.3 and 80.0%, respectively, for overall relapse detection based on patient level. Only 1 of the 8 recurrences was suspected based on PSA progression. 4 of the 8 patients with PC relapse (19%) underwent salvage therapy (2 patients by radical prostatectomy, 2 patients by salvage FT-HIFU). Conclusion: Postoperative mpMRI might play a valuable role during follow-up after focal HIFU therapy, particularly in terms of infield relapse detection. Irrespective of mpMRI results, the repeat biopsy regimen should incorporate systematic biopsy including cores of the treated and untreated prostate areas.