Login to Access Video or Poster Abstract: MP70-16
Sources of Funding: _x000D_ InSightec, Inc. Haifa, Israel; the Ontario Research Fund; and the Canadian Foundation for Innovation._x000D_

Introduction

Organ preserving therapy is emerging as an option for localized prostate cancer to minimize the morbidity associated with whole-gland therapy. We examine the short-term oncologic and functional data of the initial phase 1 trial of patients treated with focal transrectal MRI-guided focused ultrasound (MRgFUS) in North America._x000D_

Methods

This phase 1 prospective study was approved by institutional review board. Eight patients with organ-confined PC visible on multiparametric MRI (mpMRI) and confirmed by the MRI-fusion biopsy (Artemis, Eigen) were enrolled. Patients were eligible with PSA ≤10ng/mL and Gleason score (GS) ≤ 7(4+3). Tumors larger than 1.5 cm in any dimension, too peripheral for a 5mm ablation margin or with concern for extraprostatic extension were excluded. Under MRI-guidance and real-time MR thermography, focal lesions were ablated using high frequency ultrasound energy delivered via an endorectal transducer with 990 elements (ExAblate 2100, InSightec). Incidence and severity of treatment-related adverse events were recorded at 6 months. _x000D_

Results

Eight patients with 10 peripheral zone lesions were treated. Prostate volume ranged from 25 to 50 cc with mean target volume of 2.7cc (range 0.4 - 5.7cc). Mean procedure time was 248 minutes. Based on pre-treatment biopsy, six lesions were GS6(3+3), two were GS7(3+4) and two others were GS7(4+3). Treatments were all completed as planned without major technical delays or surgical complications. Mean post treatment non-perfused volume was 4.3cc (range 2.2 - 7.6cc). Quality of life parameters were similar between baseline and 6-months in 6 of 8 patients. One patient with bilateral ablation had significantly worse storage symptoms while a second patient developed self-limiting acute prostatitis with erectile dysfunction. Mean PSA decreased from 5.06 to 3.4 ng/ml at 6 months. All patients were MRI negative in their treated regions. On biopsy, five patients were disease-free in treated regions (7 of 10 lesions). In one patient with a presumed GS7(4+3) tumor, a 2mm MRI-invisible focus of GS8(4+4) PC was seen in 1 of 5 cores from the ablation site. He underwent prostatectomy with negative surgical margins.

Conclusions

MRgFUS is a feasible and safe method of ablating localized PC. Further work is required to improve patient selection and address causes of failed ablation. Our study is limited by small sample size and brief follow-up. More meaningful oncologic and functional outcomes for MRgFUS can be assessed with larger trials with longer follow-up. _x000D_

Funding

_x000D_ InSightec, Inc. Haifa, Israel; the Ontario Research Fund; and the Canadian Foundation for Innovation._x000D_