Cryotherapy, also known as cryoablation or cryosurgery, is a minimally invasive technique that uses extreme cold to destroy cancerous tissue. This procedure freezes and kills the cells within the prostate gland. It is an established option for men with organ-confined prostate cancer and is less invasive than traditional surgery.
The Mechanism of Action
Cellular destruction is caused by rapid temperature drops, typically reaching as low as -40°C in the targeted area. The primary effect is the formation of ice crystals both inside and outside the cancer cells. Intracellular ice mechanically ruptures cell membranes and organelles, causing immediate cell death by necrosis.
Extracellular ice formation draws water out of the cells due to an osmotic gradient, leading to severe cellular dehydration and an excessive concentration of salts that denatures proteins. A secondary, yet significant, mechanism involves damage to the microvasculature supplying the tumor. Freezing causes blood vessels to constrict and clot (vascular stasis), starving the tumor of oxygen and nutrients and leading to ischemic death.
The protocol involves a rapid thaw cycle following the initial freeze, which is often more destructive than the cold exposure itself. This rapid rewarming causes sudden osmotic shifts and further cellular membrane damage, ensuring the irreversible destruction of the cancerous cells. Controlled application of these freeze-thaw cycles maximizes tissue destruction while minimizing risk to adjacent structures.
The Cryosurgery Procedure
Cryotherapy is typically performed in an operating room, usually under general or regional anesthesia, such as a spinal or epidural block. The patient is positioned to allow access to the perineum (the area between the scrotum and anus) for probe insertion. The surgeon first inserts a transrectal ultrasound (TRUS) probe into the rectum to create real-time images of the prostate and surrounding anatomy.
Using TRUS guidance, thin, hollow needles called cryoprobes are inserted through the perineum and precisely placed into the prostate gland. A warming catheter is placed in the urethra and circulated with warm saline to protect the urinary channel from freezing damage. Thermal sensing probes are also strategically placed near sensitive structures, like the rectal wall and neurovascular bundles, to monitor temperature and prevent unintended tissue injury.
The cryoprobes circulate a gas, such as argon, to rapidly cool the tissue, creating an ice ball that encompasses the targeted tumor. This is followed by a thawing phase, often using helium gas, and the entire procedure usually takes between one to two hours. The freeze-thaw cycle is typically repeated twice to ensure complete cell death before the probes and TRUS device are removed.
Patient Selection and Suitability
Cryotherapy is a viable treatment for localized prostate cancer that has not spread beyond the gland. It is commonly offered as a primary treatment for men with low-to-intermediate risk cancer who prefer a minimally invasive approach. It is also suitable for those who are not candidates for radical surgery or radiation due to other health conditions.
The procedure is also a well-established salvage therapy for patients whose cancer has returned following previous radiation treatment. Patient selection involves a detailed review of the cancer’s characteristics, including its stage and grade.
Specific anatomical features can contraindicate the procedure, such as a prostate volume exceeding 50 to 60 cubic centimeters, which may make complete freezing difficult. Additionally, men who have had prior complex rectal or anal surgery or a large defect from a transurethral resection of the prostate (TURP) may be excluded due to an elevated risk of complications.
Post-Procedure Recovery and Outcomes
Patients are often discharged the same day or after an overnight stay. A urinary catheter is necessary because of temporary swelling in the prostate and urethra. The catheter typically remains in place for one to two weeks to ensure bladder drainage. Patients may experience temporary side effects, including bruising and soreness in the perineal area, as well as blood in the urine.
Long-term success is primarily monitored by tracking the Prostate-Specific Antigen (PSA) level in the blood. A successful outcome is generally associated with a low PSA nadir, which is the lowest point the PSA level reaches after treatment. Biochemical failure is defined by the Phoenix definition: a PSA level that rises more than 2 ng/mL above the lowest post-treatment value (nadir).
The most common long-term side effect is erectile dysfunction, occurring because the freezing process can damage the nerves responsible for erections that run alongside the prostate. Urinary incontinence is also a risk, though severe, long-term incontinence is rare, especially when cryotherapy is used as a primary treatment. Rare but serious complications include the formation of a fistula, an abnormal connection between the rectum and the urethra, reported in less than one percent of cases.