High-Intensity Focused Ultrasound, or HIFU, is a treatment that uses focused sound wave energy to destroy cancerous cells in localized prostate cancer. This energy generates intense heat, reaching 80 to 100 degrees Celsius, which destroys the targeted tissue while aiming to leave surrounding healthy structures unharmed.
This method is minimally invasive as it requires no surgical incisions. The energy is delivered from a probe placed in the rectum, allowing for the treatment of specific cancerous areas, known as focal HIFU, or the entire prostate gland. Its application is for prostate cancer that has not spread beyond the gland.
The HIFU Procedure
The principle of HIFU is similar to using a magnifying glass to focus sunlight. Sound waves are concentrated on the cancerous tissue within the prostate, rapidly heating and ablating the targeted cells. This creates a distinct treatment zone while minimizing heat exposure to adjacent tissues like the bladder and rectum. A cooling balloon surrounding the delivery probe helps protect the rectal wall.
Before the procedure, patients undergo preparations that may include an enema or laxative to clear the bowels. The treatment is performed under either general or spinal anesthesia to ensure the patient remains completely still. A specialized transrectal probe is inserted that emits the high-frequency ultrasound waves and simultaneously provides real-time ultrasound images of the prostate.
This live imaging allows the surgeon to map and monitor the treatment area, guiding the energy beams with precision. Pre-procedure MRI scans are sometimes fused with the live ultrasound images to enhance targeting accuracy. The length of the procedure depends on the size of the area being treated, with focal therapy taking one to two hours and whole-gland treatment lasting around three hours. Patients are often discharged the same day.
Candidate Eligibility for HIFU
Suitability for HIFU depends on several factors evaluated by a urologist. The primary consideration is the cancer’s status. HIFU is most effective for localized prostate cancer that has not spread beyond the prostate gland (stages T1-T2) and is not recommended for patients whose cancer has metastasized.
The tumor’s aggressiveness, determined by its Gleason score from a biopsy, is another factor. Ideal candidates have a Gleason score of 7 or less, which indicates a low- to intermediate-risk cancer. Prostate-Specific Antigen (PSA) levels are also assessed, with many centers preferring patients with a PSA level of 20 ng/mL or lower. These markers help ensure the cancer is contained.
Physical characteristics of the prostate gland also play a role. Because the ultrasound energy is delivered from a rectal probe, it can only effectively reach a certain distance. Men with very large prostates (often over 40 grams) may not be suitable candidates, especially if the tumor is located in the anterior portion of the gland. Significant calcifications within the prostate can also be a contraindication, as these can block the ultrasound waves.
Potential Outcomes and Side Effects
Success following HIFU is measured through ongoing monitoring, which includes regular PSA tests and follow-up biopsies. For appropriately selected patients, particularly those with intermediate-risk cancer, HIFU can be effective at controlling the disease within the treated area. A positive outcome is the preservation of quality of life, with many men returning to normal activities quickly.
Despite its precision, the treatment carries risks. Urinary issues are common in the short term. A urinary catheter is required for about five to seven days after the procedure to manage post-treatment swelling. After catheter removal, patients may experience symptoms like urinary urgency, frequency, or a slower stream, which resolve within a few weeks with medication. The risk of long-term urinary incontinence has been reported in a range of 4% to 34.4% of cases, and urinary tract infections can also occur.
Sexual function can also be affected. The risk of developing erectile dysfunction after HIFU varies widely, with studies showing rates from 13% to 90%, depending on the patient’s pre-treatment function and the extent of the procedure. For men with good baseline function undergoing focal therapy, the risk is lower, around 5% to 10%. A rare but serious complication is the formation of a recto-urethral fistula, an abnormal connection between the rectum and urethra.
Comparison with Traditional Treatments
HIFU can be compared with established methods like radical prostatectomy and radiation therapy. Each approach has a distinct profile regarding invasiveness, recovery, and side effects.
HIFU is a non-surgical procedure with no incisions, contrasting with radical prostatectomy, which is surgery to remove the entire prostate gland. Recovery from HIFU is faster, with most patients resuming normal activities within weeks, whereas recovery from surgery is more extensive. While both treatments carry risks of urinary incontinence and erectile dysfunction, studies suggest HIFU may have a lower negative impact on these functions.
Compared to radiation therapy, HIFU offers a different treatment schedule. HIFU is a single-session treatment, while external beam radiation often requires daily sessions over several weeks. The nature of the side effects also differs; HIFU uses thermal energy to ablate tissue, whereas radiation can cause damage to surrounding tissues over time. An advantage of HIFU is that it is a repeatable procedure and does not preclude other treatments like surgery or radiation if the cancer returns, which is not always the case after a full course of radiation or a prostatectomy.