Cryotherapy, or freezing, is a method of destroying prostate cancer by subjecting the prostate gland to the extreme temperature of -40° Celsius. The procedure, done under anesthesia, consists of using ultrasound image guidance to insert thin hollow needles into the prostate gland through the perineum (skin between the scrotum and anus). When argon gas is circulated in the probes (which are sealed, so no argon enters the patient’s body), the tip becomes very cold, and an iceball forms and enlarges around the tip. If the intent is to treat the entire gland, an array of 6-8 probes will be placed so that the iceballs overlap as each one grows. This is to ensure that the cold temperature will be uniform throughout the gland and no cancer cells will be missed or undertreated. The total iceball size will exceed the size of the gland by an extra safety margin to preemptively kill any tumor cells at the outer edge of the prostate capsule. After an initial freeze, the prostate is allowed to thaw, then is frozen and thawed once more. This double cycle results in destruction of the cell membrane, and disruption of the internal cell environment. Both healthy cells and cancer cells are killed, and clinical data shows that cryotherapy (or simply cryo for short) is at least as effective as radical prostatectomy in long term cancer control.
The device that delivers cryo and the way the procedure is done has certain safety measures. These include temperature sensors in and around the probes, to ensure that the temperature is uniform throughout the total iceball; and during the procedure, a warming catheter circulates warm water through the urethra into the bladder, in order to protect the lining of the urethra (tube that carries urine from the bladder to the penis) from severe damage. A special thermocouple inserted between the prostate gland and the rectal wall monitors the temperature to make sure that the iceball does not damage the rectal wall, which could result in a hole called a fistula. Fistulas were more common in the early days of cryo (mid-1990s) but today they are almost nonexistent thanks to improved safety.
Because of its effectiveness, patients with multifocal or aggressive prostate cancer may choose cryo if they can’t have or don’t want surgery or radiation. Its appeal lies in the fact that it is an outpatient, minimally invasive procedure. However, cryo has potential side effects that patients need to be aware of.
Whole-gland cryo leaves almost all patients impotent because the additional iceball margin will encompass the nerve bundles that “hug” the edges of the gland. These nerves control erections, and the lethally cold ice damages them. In some cases, the nerves may slowly regenerate. However, fewer than half of patients may eventually be able to have erections with the aid of a vacuum device or medications like Viagra, and this can take anywhere from several months to 3 years. One center that offers cryo advises their patients, “Even if an erection and climax is achievable after cryoablation of the prostate, there will be very little or no ejaculate. This is because the glandular prostatic tissue is replaced with scar like tissue.”[i] Because of high impotence rates, cryo is generally viewed as a better treatment option with patients for whom sexual activity is not a priority.
With regard to urinary side effects, the warming catheter offers some protection for the small urinary sphincter muscle that controls urination. However, according to the American Urological Association, “The incidence of permanent physician reported incontinence (wearing a pad) in the literature ranges from <1% to 8%.”[ii] A more common urinary side effect is sloughing, or shedding of dead cells from the lining of the urethra. Most cases of sloughing are minor and short-lived, though it can be uncomfortable and alarming to see discolored (brown or red) urine or very small shreds of dead tissue during urination. Occasionally, sloughing can cause severe obstruction resulting in voiding problems (retention, straining, slow stream, sense of urgency, or incontinence). A procedure called a TURP or “reaming out” may be necessary to alleviate the obstruction.
Aside from the swelling and tenderness that usually last for a few days after the procedure, other but less common side effects of cryo can occur: numbness or tingling of the penis, and scrotal swelling have been reported in the literature.
Finally, because the size and shape of the iceball can be controlled by modifying the number and placement pattern of the probes, cryo can be offered as a partial or focal treatment for qualified patients. However, given the high resolution and clarity of magnetic resonance imaging, MRI-guided focal laser ablation (FLA) offers not only a precisely targeted way to destroy prostate tumors, but also minimal to no risk of sexual dysfunction, incontinence or sloughing. This may account for the increasing appeal of FLA as we are experiencing at the Sperling Prostate Center.