What is cryoablation?
Cryoablation is a form of cryotherapy for the prostate that involves the controlled freezing of the prostate gland in order to destroy cancerous cells. The damage caused by freezing occurs at several levels: molecular, cellular, and whole tissue. Important factors influencing freezing injury are the rate of temperature reduction after the initiation of freezing, the time cells remain frozen, and the subsequent heating rate during thawing.
The cells are not the only structures damaged during freezing. During cryoablation of the prostate, the surrounding connective tissue (stroma) and the smallest blood vessels (capillaries) are damaged and subsequently have an inadequate blood supply that is believed to slow the growth of cancer.
Who are the most suitable candidates for cryoablation of the prostate?
Suitable candidates for this procedure are patients who have organ-confined prostate cancer or those who have minimal spreading beyond the prostate.
How is the procedure performed?
Under anesthesia, an ultrasound probe is guided into the rectum. The prostate is imaged and its dimensions measured. An aiming grid software program is then activated, and images of the prostate are projected on a screen. Under continuous monitoring with ultrasound imaging, cryoablation probes are placed at predetermined sites within the prostate. The freezing is started at the front part of the prostate by activating the front probes, followed by the middle, and finally the back probes. This sequence allows continuous monitoring (with the freezing process visualized through the transrectal ultrasound). Two freezing cycles usually are carried out. Between them, the prostate is allowed to thaw either passively or actively with the use of helium gas. If the prostate is more than 26 to 27 mm long, an apical pullback maneuver is used to freeze the lower part of the prostate. Double freezing is performed again.
The urethra is kept warm during prostate freezing so that the urethral wall remains viable. This is important, as it minimizes the risk of urethral damage, obstruction, and urinary incontinence. The bladder and urethra are examined meticulously with a flexible cystoscope for evidence of injury. If a probe is found piercing the urethra, it is repositioned. A suprapubic catheter (a small catheter that is placed in the bladder through a small opening in the lower abdomen) is inserted and secured in place by a suture. The urethral warming catheter is introduced through the urethra with its end in the bladder.
During the procedure, the bladder is kept nearly full by keeping the open suprapubic catheter at a slightly higher level than the bladder. The urethral warming catheter keeps the urethra warm throughout the procedure and remains active for about 20 minutes after complete thawing to prevent damage to the urethra.
What can be expected after treatment?
The patient generally is kept overnight, offered some food, and encouraged to walk. The patient usually is discharged the next morning with a catheter in place for drainage.
The patient can attempt to urinate at first desire. Most patients are able to urinate in about 10 to 15 days, but some may require longer recovery periods. When the patient is able to urinate well and empty the bladder satisfactorily, the catheter is removed. Oral antibiotics are usually given for 10 to 14 days. Other temporary symptoms the patient may experience are generalized fatigue that usually persists for seven to 10 days, urethral discharge, scrotal swelling, numbness at the tip of the penis, passage of flecks of tissue, pain or burning sensation during urination, and increased urinary frequency and/or urgency.