Ultima Vez Modificado: 20 de octubre del 2007
Dear OncoLink "Ask The Experts,"
Carolyn Vachani RN, MSN, AOCN, OncoLink's Nurse Educator, responds:
Cryotherapy is a procedure that uses freezing and thawing to kill cancer cells. This technique has been used to treat skin cancers for some time, but the experience with prostate cancer is not as well defined. Most doctors consider good follow up data for prostate cancer treatment to be in the neighborhood of 15-20 years since treatment. This means patients have been followed for 15-20 years since treatment to evaluate for recurrence. Follow-up for cryotherapy has only reached 7 years, and this is not in the context of a clinical trial. It is estimated that from 1996-2005 only 2% of prostate cancer patients were treated with cryotherapy in the U.S.
The procedure set-up is similar to that used for brachytherapy. The patient receives spinal (epidural) anesthesia, needles are inserted into the prostate through the skin between the scrotum and rectum and the patient typically goes home the same day or stays one night in the hospital. With cryotherapy, probes are inserted into the needles in the prostate. The probes initially rapidly freeze the tissue, and then rapidly thaw the tissue. This freeze and thaw cycle may be repeated (two cycles have led to better outcomes). As first-line treatment, the best outcomes are seen in patients with low-risk tumors (PSA<10, Gleason < 6, stage T1c-T2a). Cryotherapy may also be used as salvage therapy in patients whose disease has recurred after surgery or radiation therapy, although this must be limited to non-metastatic disease (no spread elsewhere in the body). In addition, the size of the prostate must be a consideration in this therapy because the needles must be able to reach all areas of the tissue.
Although there are no randomized clinical trials and the number of patients treated is small, some side effects have been consistently identified. Impotence is estimated to occur in 40-100% of patients, with about 5% regaining potency in the months following treatment. Urinary incontinence rates vary greatly depending on how the investigator defined incontinence. The best estimate is 5% when cryotherapy is used as first line treatment and 10% when used as salvage therapy. Other urinary tract symptoms are caused by the lining of the tract being affected by the freezing/thawing cycles. This can lead to tissue sloughing causing pain, infection, urinary retention, and in rare cases, surgery may be required to remove the tissue. This side effect can be lessened with the use of a heated urinary catheter during the cryotherapy procedure. Pelvic and rectal pain is reported in as many as 11% of patients, but the cause is unclear. Rectourethral fistula is a relatively rare complication in which a cavity develops connecting the urinary tract to the rectum. A fistula may require surgery, but can often heal on its own with a urinary catheter in place.
The relapse rates following cryotherapy vary greatly depending on tumor features (PSA levels, Gleason scores, stages) and which review of the treatment you read. No randomized clinical trials have been performed to assess the success of this treatment, making it tough to compare to other therapies. Some institutions have reported their experience with relapse rates, but these are difficult to interpret in the absence of a controlled trial.