Prostate Cryoablation
Prostate cryoblation is a primary treatment option for prostate cancer that involves delivering precise doses of extremely cold gas into the prostate to destroy diseased tissue, while sparing surrounding structures such as the bladder and urethra
It is well known that when human tissue is exposed to temperatures below freezing that tissue damage occurs. With temperatures falling to -7° to -10° Celsius extra- cellular water (water in tissue but outside cells) begins to crystallize. This in turn increases the concentration of electrolytes in the extracellular fluid and begins to draw water from inside cells. As the temperature drops to °-15C ice crystals begin to form inside the cells. Cell membranes are damaged, and cells are destroyed. When tissue is cooled to -40°C, all metabolic processes stop.
Cryoablation in Clinical Practice
The original indication for cryoablation of the prostate was for salvage therapy in prostate cancer patients who had recurred after either external beam radiotherapy or brachytherapy. However, now prostate cryotherapy is also indicated for primary treatment of prostate cancer. As described in the Prostate Cancer section of this site, Dr. Engel does not feel cryotherapy to be appropriate for all cases of prostate cancer. A typical patient is an older patient, particularly one with voiding symptoms that prohibit the safe application of radiation. Other indications would include lower risk cancers, and in patients with morbidities that would make surgery exceedingly risky.
The technological leap forward that allowed for prostate cryotherapy was the development of 3mm cryoprobes, and soon after even smaller, 1.47 mm cryoprobes. These new probes made the freezing process far more controlled and precise. Cryoprobes are special hollow needles that allow for the flow of super cooled gas. When used with thermocouples, needles that measure tissue temperature at all of the vital structures around the prostate (urinary sphincter, erectile nerves, etc.), the prostate can undergo freezing in a very controlled manner. Transrectal ultrasound is used for this procedure, so the surgeon has not only temperature feedback but also real time visual feedback that ensures that the entire prostate is treated while sparing structures such as the rectum and bladder. Nerve sparing cryotherapy can be performed, and this technology is not generally limited by prostate size.
The entire prostate, except for the urethra which is warmed during the procedure, is frozen during the procedure. This kills most of the tissue in the prostate, although the capsule and some fibrous tissue does remain which preserves urinary function. . The performance of prostate cryotherapy is very similar to prostate brachytherapy, and the same needle template is used. However, where seeding takes up to 30 needles, cryotherapy uses only 6-8. Dr. Engel prefers cryotherapy to seed implantation because he feels that the treatment is far more controlled, tailored, and immediate with fewer side effects than seeds. The cure rate of prostate cryo is very similar to seed implantation or radiation in general. Another positive of cryotherapy is that if one does recur, a patient may be treated again, whereas with radiation one cannot be radiated a second time safely.
There are other distinct advantages of cryotherapy that some men find very appealing. Dr. Engel performs prostate cryotherapy in an outpatient, surgery center setting. Patients will require a catheter for a similar period of time as robotic prostatectomy (6 days), but will not experience the period of mandatory incontinence that comes with surgery. The incontinence rate of cryotherapy is similar to radiation at 1-2%, but unlike radiation, incontinence after radiation can easily be corrected if it occurs since the surrounding tissue remains viable. There is little pain or recovery associated with cryotherapy, with the primary patient complaint after cryotherapy being scrotal swelling. If nerve sparing is not performed (only indicated in low risk cases), patients will suffer similar setbacks to their erectile function as seen with surgery. Erections often do return after a year or so, depending as with surgery on age, blood flow, previous erectile function, interest etc..
One day prior to the procedure, the patient is instructed to start taking a quinolone antibiotic (levaquin or cipro), undergo a bowel preparation, and assume a low fiber diet. On the day of the procedure, either general or spinal anesthesia is required. With the patient in lithotomy position, a urethral warming catheter is placed so that the urethra is spared, as well as the cryoprobes and thermocouples. These needles are placed through the perineal skin between the scrotum and rectum under ultrasound guidance using a special template, much the way that seeds are placed for brachytherapy. Two freeze-thaw cycles are completed, after which time a catheter is placed in the bladder. Prostate cryotherapy takes around an hour to perform, and there is little pain afterward. For the first hour or two, a patient will commonly feel an urge to urinate which slowly dissipates. There can be blood in the urine of course, and as stated scrotal swelling is very common and should not concern the patient. The patient will be asked to remove his catheter six days later and see Dr. Engel for a voiding trial the next day. Occasionally, especially in those with pre-existing urinary difficulties, the catheter must be replaced temporarily.
Risks of Prostate Cryoablation
Complications of cryoablation of the prostate are generally local, and can rarely include urethral sloughing leading to blood in the urine and urinary burning, very rare incontinence, infection, penile numbness, and erectile dysfunction. The incidence of incontinence is 1-2% in primary cases, and slightly higher in radiation salvage cases.
Results of Prostate Cryoablation
The PSA will rise sharply during the immediate post freeze period, and should not be checked. This elevation is thought to be due to the release of intracellular PSA at the time of cell destruction. The PSA will usually get to its lowest point (nadir) at 3-6 months. Ideally, the nadir will be <0.4. In one 7-year study, the biochemical disease free survival rate for low grade, intermediate, and high grade prostate cancers, was 61%, 68% and 61%. When the PSA nadir point was placed at <1.0 the rates were 87%, 79%, and 71%.
To determine if you are a candidate for cryoablation, or to discuss anything at all about prostate cancer, call and arrange a consultation with Dr. Engel. Dr. Engel takes pride in realizing that one size does not fit all. We are able to offer all of the latest treatments for prostate cancer, and will attempt to help you decide what is best for you based on your age, stage and grade of prostate cancer, as well as your other medical problems.
