High-intensity focused ultrasound in the treatment of prostatic tissue.

OBJECTIVE Beginning in 1987, high-intensity focused ultrasound was investigated in the canine model to determine the feasibility of destroying prostate tissue. After demonstrating the ability to ablate prostate tissue reliably in a canine model, a 15-patient pilot clinical study was undertaken at Indiana University in the fall of 1992. This pilot study was undertaken to assess the safety in the human clinical situation, as well as to give some early efficacy results. METHODS The early canine feasibility studies were conducted via a suprapubic extracorporeal approach using two separate transducers, one for imaging and the other for therapy. Subsequent to this, a transrectal probe, which had the dual capability of both imaging and therapy, was developed and used to treat canine prostates in a formal, "good laboratory practice" study to determine the safety of this technology prior to beginning treatment of human benign prostatic hypertrophy. RESULTS The formal canine studies demonstrated that prostatic tissue could be reliably ablated in the therapy zone. The dosimetry and duty cycle required to ablate canine prostatic tissue effectively was also determined in this study. The study also demonstrated that the prostatic tissue could be ablated without injury to the intervening rectal tissue or periprostatic tissue. The human pilot study has also demonstrated safety of high-intensity focused ultrasound, as well as early efficacy. CONCLUSIONS These early clinical results are encouraging, but assessment of efficacy will require a randomized study comparing high-intensity focused ultrasound to sham and to transurethral prostatectomy. This multicenter trial is currently planned.