Purpose: We conducted a phase I/II study to evaluate the efficacy of transrectal high intensity focused ultrasound in the treatment of localized prostate cancer and to assess associated complications. The efficacy of a new high intensity ultrasound device was evaluated using post-treatment prostate specific antigen (PSA) levels and histological results from prostate biopsies as end points.
Materials and methods: A total of 113 transrectal high intensity focused ultrasound sessions were performed in 50 patients with localized prostate cancer, who were not suitable candidates for radical prostatectomy. Of these patients 2 underwent salvage ultrasound treatment for locally recurrent cancer following definitive radiation therapy. Mean plus or minus standard deviation patient age, PSA and prostate volume were 70.7+/-4.54 years, 9.61+/-7.42 ng./ml. and 37.3+/-19.1 cc. The 2 different high intensity ultrasound prototypes were successfully used, and the latter prototype included several safety devices to reduce morbidity. Median followup was 24 months (range 3 to 46). Control parameters were changes in PSA and random control sextant biopsies at 1 to 3, 3 to 12, 12 to 24, 24 to 36 and 36 to 48 months.
Results: For the evaluation of therapy patients were divided into 4 groups. Group 1 (complete response) included 28 patients (56%) with no residual cancer and PSA less than 4 ng./ml. (mean 0.93), group 2 (biochemical failure) 3 patients (6%) with no residual cancer and PSA greater than 4 ng./ml. (mean 6.22), group 3 (biochemical control) 9 patients (18%) with residual cancer (mean positive biopsy 1.1 of 6) and PSA less than 4 ng./ml. (mean 0.90), and group 4 (failures) 10 patients (20%) with residual cancer (mean positive biopsies 1.9 of 6) and PSA greater than 4 ng./ml. (mean 8.9). Of the 10 cases in group 4 hormone therapy was required in 3 and radiotherapy in 5. Complication rate with the first prototype device was 50% and it decreased to 17% with the second prototype.
Conclusions: Morbidity associated with high intensity focused ultrasound treatment is currently minimal. Local control of the localized prostate cancer was observed in groups 1, 2 and 3 (80%). Repeat sessions were deferred in groups 2 and 3 based on changes in PSA. These preliminary data suggest that high intensity focused ultrasound represents a valid alternative treatment strategy for patients with localized prostate cancer who are unsuitable for surgery.