The three pillars of cancer treatmentsurgery, chemotherapy, and radiationare being augmented and in some cases replaced by a new twist on an old idea: destroying tumors by flash freezing.
Debuting in the 1960s, cryosurgery was initially viewed as a promising new method of attacking cancer cells, but clinicians soon discovered they had difficulty guiding and controlling the freezing process. Such imprecision often resulted in the destruction of too much adjacent normal tissue, and the technique was quickly abandoned.
But by marrying military technology developed to cool missile guidance systems with advances in medical imaging such as ultrasound, computerized tomography, and magnetic resonance imaging, cryosurgery is emerging as not only a viable but in some cases a more favorable alternative for treating cancers of the prostate, breast, liver, and kidney.
Less Invasive Approach
"In the last 2 years there has been a change in the mentality of doctors, and I see this as continuing as the whole field moves toward minimally invasive procedures," said Aaron Katz, M.D., assistant professor of urology at Columbia Universitys College of Physicians and Surgeons. "The old-time urologists who think the only way to cure cancer is with a knife are a dying breed."
Cryosurgery of the prostate is generally done at temperatures below 40°C with the use of hollow probes that are inserted into the gland to deliver and circulate a freezing agent, liquified argon gas, directly to the tumor and affected tissues. As a ball of ice crystals begins to form around the tips of the probes, a warming catheter inserted through the urethra protects surrounding tissue.
The procedure requires precise placement of the probes using imaging technology, and thermosensors can be used to monitor tissue temperatures while a "freezing-thawing" process is repeated before the probes are withdrawn. The procedure takes about 2 hours, and the dead prostate tissue shrinks and is dissolved naturally.
In July 1999, the U.S. Health Care Financing Administration granted Medicare reimbursement for cryosurgical procedures involving primary, localized prostate cancer after reviewing evidence that the procedure is safe, effective, and comparable to radiation therapies such as external beam and brachytherapy (the implantation of radioactive pellets or "seeds" in the prostate gland).
In addition, proponents maintain that because the procedure is less invasive and time consuming than other approaches there are fewer risks, faster recovery, less morbidity, and a high degree of cost-effectiveness.
Cost and Outcome Advantages
According to HCFA, the cost of prostate cancer cryosurgery is approximately $13,500, compared with $14,200 for brachytherapy, $15,000 for external beam radiation and at least $10,600 for radical prostatectomy. Prior to Medicare approval, about 80 private insurers offered coverage for cryosurgery with about 10% limiting reimbursement to radiation failure. Still, more than 75% of all treatments last year were for initial versus "salvage" treatment following radiotherapy. With more than 80% of those diagnosed with prostate cancer older than 65 years and 16 million male Medicare beneficiaries, the market potential is enormous.
Katz, who is also a clinician at New Yorks Columbia-Presbyterian Medical Center, has performed more than 200 of the procedures, noting that referrals from community physicians for patients with localized tumors are increasing as patients demand less invasive treatment.
Cryosurgical ablation uses a minimal amount of anesthesia, it kills tumors growing outside the prostatic capsule, and blood loss is minimal, Katz said. In addition, it usually requires only an overnight hospital stay and patients can often resume normal activities within a few days.
Five-year-survival rates appear at least comparable to other treatment modalities, and rates of urinary incontinence sometimes associated with radical prostatectomy and external beam radiation are reduced from at least 23% and 10%, respectively, to approximately 1% to 4% similar or better than brachytherapy estimates.
Perhaps even more important, it is not only repeatable but can be a viable option among patients who are poor candidates for surgery or radiation due to their age or because they have other chronic conditions such as heart disease.
But existing freezing technologies do affect the neurovascular bundle. At least half of those treated report impotence as the most prominent side effect, while about 22% to 29% of those undergoing external beam radiation, 60% to 89% of those undergoing radical prostatectomy, and up to 50% of those undergoing brachytherapy report a similar outcome.
Breast Cancer Application?
It now appears that cryosurgical technology may have even broader applications. Last month a Canadian team reported that using cryosurgery to treat breast cancer in women who were referred for breast surgery resulted in total destruction of the tumors in eight of nine women and partial tumor destruction in the remaining patient.
Study investigator Christian Moisan, Ph.D., head of the interventional MRI program at Quebec City University Hospital, cautioned that while the sample size is quite small and results are very preliminary, they are nevertheless extremely encouraging.
"What we really care about is being able to predict assuredly that the cancer has been completely destroyed using the technique, and we are finding that we have been able to anticipate complete destruction of the tumor with a high degree of success," Moisan said.
The study is limited to women with localized breast cancer who agree to delay surgery for one month to undergo the cryosurgical procedure using interventional MRI guidance. One month later they undergo scintillation mammography to determine the extent of tumor destruction, and then standard treatment, such as lumpectomy or mastectomy with adjuvant treatment, is resumed. Images of the breast after cryosurgery and after standard surgeries are then compared.
The breast cryosurgery procedure takes about 3 hours with 1 hour for recovery and can be done on an outpatient basis, Moisan said.
Liver, Renal Cancers
Cryosurgerys most dramatic benefit may be in those who cannot undergo standard surgical treatment because of their age or other debilitating conditions and in cases of inoperable liver cancers, which is among the other avenues Moisans team is pursuing.
"There is a very strong need for new curative options for patients who would otherwise face a grim course," Moisan said. "New applications like MRI-guided cryosurgery of the liver are becoming viable options for those who would otherwise have none."
In addition, similar technology was used to perform the first renal cancer cryosurgery using interventional MRI at the University of Mississippi in May 1999. The localized tumor of a 72-year-old man was ablated by freezing followed by laser warming while clinicians watched the tissue being destroyed in real time. The patient had one kidney surgically removed due to the same cancer in 1997, and his only alternative was the surgical removal of his remaining kidney. He was discharged the following day and allowed to resume normal activities almost immediately.
At present only a handful of companies are in the cryosurgical market. These include Irvine, Calif.-based Endocare Inc., Galil Medical Ltd. of Israel, and Cryomedical Sciences Inc. of Rockville, Md.
|
|
![]() |
||||
|
Oxford University Press Privacy Policy and Legal Statement |