How is the cryotherapy procedure performed?

Marc B. Garnick, MD
Hematology & Oncology
When cryotherapy is used to treat prostate cancer, a physician guides several small needles into the patient's prostate gland through the perineum while the patient is under anesthesia. To accurately position the needles and tailor the treatment to the tumor's shape and location, the physician relies on real-time images of the prostate generated by an ultrasound probe inserted in the rectum. To help protect the urethra from freezing, the physician inserts a warming catheter. This also helps keep dead tissue from blocking urine flow later on. Similarly, the physician inserts warming needles into the tissue between the prostate and the rectal wall to prevent damage to the rectum.

During modern cryotherapy, a physician inserts several thin needles into the prostate. The needle tips are rapidly cooled to -40 degrees Celsius with argon gas, which freezes prostate tissue and destroys cancer cells. A rectal ultrasound probe generates real-time images that allow the physician to monitor cycles of freezing and thawing. Warming needles inserted between the prostate and rectal wall prevent damage to the rectum.

During the procedure, the cryotherapy unit super-cools the needle tips in the prostate with argon gas. (Early prostate cryotherapy used liquid nitrogen for freezing, which necessitated the use of thicker probes. Today's thinner needles and the use of a gas instead of a liquid allow for greater treatment precision.) For cryotherapy to be as effective as possible, tissue must be rapidly frozen -- temperatures plunge to about -40 degrees Celsius -- and then slowly thawed at least twice. As sharp, jagged ice crystals form inside the cells, they tear the cells apart. Cells may also burst when they swell and shrink during the repeated cycles of freezing and thawing. Ice forms inside the small vessels feeding the tumor, too, choking off its blood supply. To determine when tissue has been sufficiently frozen, the physician checks ultrasound images of the prostate and monitors the temperature in and around the gland.

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