Magnetic resonance guided focused high frequency ultrasound ablation for focal therapy in prostate cancer - phase 1 trial

Objectives: To evaluate the feasibility and safety of focal therapy for low-intermediate risk prostate cancer (PCa) with magnetic resonance-guided high frequency focused ultrasound (MRgFUS) METHODS: This IRB-approved phase 1 prospective study enrolled eight patients with prostate specific antigen (PSA) ≤ 10 ng/ml, ≤ cT2a and Gleason score ≤ 7 (4 + 3) disease following informed consent. Under MRI guidance, focused high frequency ultrasound energy was delivered to ablate the target tissue. Treatment-related adverse events were recorded. Oncologic outcomes were evaluated with multiparametric MRI, PSA and TRUS biopsy at 6 months following treatment.

Results: Ten target lesions [six Gleason 6 lesions, two Gleason 7 (3 + 4) and two Gleason 7 (4 + 3)] were treated in eight men (prostate volume range, 25-50 cc; mean MRI time, 248 min per patient; mean sonication duration, 65 min). Mean target volume was 2.7 cc and mean post-treatment non-perfused volume was 4.3 cc. Quality of life parameters were similar between baseline and 6 months in 6/8 patients. All treated regions were negative on MRI; 4/8 patients and 6/10 target lesions (60%) were clear of disease on biopsy. One patient with 2-mm Gleason 8 disease in one of five cores from treatment site (4 + 3 disease at baseline) subsequently underwent prostatectomy with negative surgical margins. Three patients with low volume (5-15%) Gleason 6 residual disease were offered active surveillance. Mean PSA decreased from 5.06 at baseline to 3.4 ng/ml at 6 months.

Conclusion: MRgFUS is a feasible and safe method of noninvasively ablating low-intermediate risk PCa with acceptable short-term oncologic outcomes.

Key points: • Focal therapy selectively ablates locally confined, clinically significant index lesion with a margin while sparing rest of gland and adjacent vital structures. • Magnetic resonance-guided focused high frequency ultrasound surgery (MRgFUS) combines MRI with HIFU. • MRgFUS provides ability to monitor treatments in real time and allows a targeted approach for focal ablation. • MRgFUS is a feasible, safe method of noninvasively ablating low-intermediate risk PCa. • MRgFUS provides acceptable oncologic outcomes at 6 months.