HIFU therapy and cryodestruction are minimally invasive treatments for prostate cancer

Just a few years ago, the only option available to a urologist and oncologist for prostate cancer was bilateral orchidectomy. In the early 1990s of the last century, the proportion of early forms of cancer increased significantly in the United States and European countries, both among young people and among the elderly and senile.

More and more often the final choice of treatment method was influenced by the patient's opinion. Patients should receive complete reliable information about possible treatment options and have the opportunity to choose. Quite often, patients prefer slightly less effective, but more gentle methods than traumatic prostatectomy. This served as an impetus for the development of new effective minimally invasive techniques.

Cryo- and ultrasound destruction of the tumor have been proposed as an alternative to prostatectomy and radiation therapy for localized prostate cancer. The latter method has been included in the recommendations of the French Urological Association, and cryodestruction in the recommendations of the American Urological Association. Both methods are considered minimally invasive interventions and, theoretically not inferior to surgery and radiation, are associated with a lower risk of complications.

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Cryodestruction of prostate cancer

The following mechanisms of cell death during freezing are known:

• dehydration associated with protein denaturation;
• rupture of cell membranes by ice crystals;
• slowing of blood flow and capillary thrombosis with impaired microcirculation and ischemia;
• apoptosis.

Under transrectal ultrasound control, 12-15 cooling needles with a diameter of 17 G are inserted into the prostate gland. Temperature sensors are installed at the level of the bladder neck and the external sphincter of the rectum, and a heater is inserted into the urethra. Two freezing and thawing cycles are performed (the temperature in the thickness of the gland and in the area of the vascular-nerve bundles reaches -40 °C).

Cryodestruction is best performed on patients with a low oncological risk. The gland volume should not exceed 40 cm3 ⁽ otherwise, in order to avoid inserting freezing needles under the pubic symphysis, hormone therapy is started), the PSA level should not exceed 20 ng/ml, and the Gleason index should not exceed 6. Since there is virtually no data on 10- and 15-year remote results, patients with a life expectancy of more than 10 years should be informed that the remote results of the method have not been sufficiently studied.

When talking about the effectiveness of various new treatments, it is important to remember that the risk of death from localized PCa within 10 years after prostatectomy is only 2.4%.

It is difficult to evaluate the effectiveness of cryodestruction based on the dynamics of PSA levels, since the criteria for relapse are different when using different equipment. For example, when using second-generation equipment in a group of 975 patients, the 5-year relapse-free survival in the low, medium and high-risk groups was 60, 45 and 36%, respectively (if a relapse is considered to be an increase in the PSA level of more than 0.5 ng/ml) or 76, 71 and 61% (if a relapse is considered to be a PSA level of about 1 ng/ml). The use of the criteria of the American Society for Therapeutic Radiology and Oncology (ASTRO), where a relapse is considered to be three consecutive increases in the PSA level, demonstrates a 7-year relapse-free survival in 92% of patients.

Cryodestruction with preservation of the cavernous nerves is possible by freezing the half of the gland that is affected by the tumor.

Erectile dysfunction occurs in approximately 80% of patients (regardless of the technique used). When using third-generation equipment, tissue rejection occurs in 3% of patients, urinary incontinence - in 4.4, urinary retention - in 2, pain in the lower abdomen - in 1.4% of patients. The risk of developing a urinary fistula does not exceed 0.2%. In approximately 5% of cases, obstruction of the urethra occurs, requiring transurethral resection of the prostate gland.

According to the survey, most functional disorders caused by cryodestruction disappear within a year. In the following two years, no reliable changes occur. Three years after cryodestruction, 37% of patients can have sex.

Cryodestruction is possible in low-risk (T _1-2a, Gleason index less than 6, PSA level less than 10 ng/ml) and medium-risk (T _2b PSA level 10-20 ng/ml or Gleason index 7) groups. The volume of the prostate gland should not exceed 40 cm ³.

Five-year disease-free survival in the low-risk group is lower than after prostatectomy, but long-term outcome data are lacking and patients should be advised of this.

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High Intensity Focused Ultrasound Ablation of the Prostate (HIFU Therapy)

High-intensity ultrasound waves destroy the tumor using heating and acoustic cavitation. The tumor is heated to 65 °C, which causes coagulation (dry) necrosis. The procedure is performed under general or spinal anesthesia, in the lateral position. Destruction of each 10 g of gland tissue takes about 1 hour.

As in the case of cryodestruction, the interpretation of the results of ultrasound destruction is complicated by the lack of generally accepted criteria for effectiveness. In addition, the literature data allows us to judge studies conducted on only 10 thousand patients.

Almost all patients experience urinary retention, which requires bladder catheterization for 7-10 days or epicystostomy for 12-35 days. Mild or moderate urinary incontinence under stress is noted by 12% of patients. Transurethral resection of the prostate gland or bladder neck dissection are often necessary to eliminate urethral obstruction. Simultaneous performance of both procedures is considered optimal. The risk of impotence is 55-70%.

HIFU therapy and cryodestruction can be an alternative to surgery in patients with a life expectancy of less than 10 years or when it is performed at the patient’s request.