Cryoablation May Have Limited Role in Prostate Cancer Treatment

CHICAGO--Prostate cancer experts continue to seek other forms of therapybecause the two major treatments--radiotherapy and radical pros-tatectomy--donot always reliably eradicate malignant cells.

Cryosurgery is not a viable alternative, however, because of its highfailure rate in patients with localized cancer, said Ralph W. deVere White,MD, professor and chair of the Department of Urology, the University ofCalifornia, Davis, Medical Center in Sacramento.

When he was asked to discuss the case against cryosurgery at the ProstateCancer Shootout II, Dr. deVere White said that at first he had preparedonly mild criticism. "One hates to be a naysayer about something thatis new and not fully tested, so I came here prepared to say we need topursue it." However, data reported by Jeffrey K. Cohen, MD, who spokein favor of cryoablation, convinced him that cryotherapy is "dead."

Dr. Cohen's data showed that for men with a Gleason score of 6, PSAlevel below 10 ng/mL, and clinical grade of T2a, cryosurgery achieves a60% cure rate. "When you go from an 85% to 90% cure rate for radicalprostatectomy to 60% with cryosurgery in your favorable group of patients,this debate is over," Dr. deVere White said.

Dr. Cohen, associate professor of urology, Allegheny University of theHealth Sciences, Pennsylvania, said that cryo-surgery is not his firstchoice for men in the favorable prostate cancer population. "For aman under the age of 65 with localized disease, radical prostatectomy isat the top of my treatment list, and cryosurgery is at the bottom,"he said.

Dr. Cohen insisted, however, that cryosurgery does have a role in menwith unfavorable prostate cancer presentations, such as those who haveextrapros-tatic disease; those in their mid-50s who failed radiotherapy;or those who are not candidates for radiotherapy because of previous radiotherapyfor rectal cancer, pelvic trauma, or kidney transplantation.

Dr. Cohen acknowledged that the first 100 patients he treated with cryosurgerytended to have high rates of biopsy failure; the overall positive biopsyrate was 37% two years post-treatment. The last 100 patients treated, however,had a positive biopsy rate of only 10% two years after cry-osurgery, whichindicates how results improve with expertise.

Nevertheless, a 60% biochemical cure rate (PSA level of 0.4 ng/mL orless) at six years is the "best we can do" with cryosurgery formen with favorable presentations of prostate cancer, Dr. Cohen said.

In the unfavorable group, one third of patients had PSA of 0.4 ng/mLor less at two years. These figures nevertheless stand up well in comparisonwith the results of treatment with external beam radiotherapy, Dr. Cohensaid.

Cryosurgery performed better than external beam radiotherapy for menin the unfavorable population in a recent study at Allegheny General Hospital(Urology 45:624-663, 1995), he said. External beam radiotherapy in thatstudy had a 51% positive biopsy rate in the first three years after treatmentversus 28% for cryosurgery.

As Salvage After Radiotherapy

Cryosurgery also may be tried in men in the unfavorable group whosecancer persists after radiotherapy, Dr. Cohen suggested. "These menrepresent a special challenge, because they weren't good candidates fortreatment in the first place, and they have metastases," he said.With a biopsy failure rate of 34.3% more than two years after radiotherapy,cryosurgery can salvage one in five of these patients, which is "notgood but not bad," he said.

Dr. Cohen continues to test this form of therapy because he believesit is as good as or better than external beam radiation for men with advancedprostate cancer. "The results are good for stage C or higher prostatecancer, and the quality of life is about the same. That is why we persist,"Dr. Cohen concluded.