What is High Frequency Ultrasound (HIFU)?

Last Modified: October 20, 2007

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Question

Dear OncoLink "Ask The Experts,"
What is High Frequency Ultrasound (HIFU)?

Answer

Carolyn Vachani RN, MSN, AOCN, OncoLink's Nurse Educator, responds:

This technique uses focused ultrasound to heat small segments of the prostate. Hyperthermia units with similar heating effects were tried in the past and failed, but this new approach may result in better outcomes. Most doctors consider good follow up data for prostate cancer treatment to be in the neighborhood of 15-20 years after treatment. This means patients have been followed for 15-20 years since finishing treatment looking for evidence of recurrence. This therapy is relatively new and has not been studied in large clinical trials, therefore data and follow up time is limited.

The technique is being used in several countries outside of the U.S. , but is not yet approved for use by the U.S. Food and Drug Administration. The procedure utilizes epidural (spinal) anesthesia and is performed on an outpatient basis. A probe is inserted into the patient's rectum, allowing the physician to take ultrasound images, which are used to plan the treatment. The probe is then reinserted into the rectum and used to heat the prostate tissue. The tissue is then cooled. The entire procedure takes approximately 2-4 hours.

Five to ten percent of patients do not respond to the heating and are then excluded from therapy and some patients required 2 or 3 sessions to achieve results. In some of the reported studies, these patients were not counted as treatment failures, which affects interpretation of results. As for side effects, studies have reported impotence in 28-53% of patients and incontinence in 0-5.8% of patients. Rectourethral fistula is a relatively rare complication where a cavity develops connecting the urinary tract to the rectum. A fistula may require surgery, but can often heal on its own with a urinary catheter in place. In one study, 12% of patients required surgery to clear out an intravesicular obstruction, a result of vesicle tissue death. It is difficult to generalize with regards to side effects given the small numbers of patients and the lack of controlled trials.

The average follow-up of survivors in most series is less than 22 months, which is too short to evaluate long-term control of the tumor. The technique is best used in stage T1c or T2a tumors, with poor results in T2b and T2c cancers. There are also somewhat better results with a PSA <10 as opposed to PSA >20. There did not appear to be a Gleason score effect on outcomes. HIFU may play a role in treatment of recurrences after radiation therapy or cryotherapy, but its role in primary therapy is unproven as of yet.



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