CHICAGO--Prostate cancer experts continue to seek other forms of therapy because the two major treatments--radiotherapy and radical pros-tatectomy--do not always reliably eradicate malignant cells.
Cryosurgery is not a viable alternative, however, because of its high failure rate in patients with localized cancer, said Ralph W. deVere White, MD, professor and chair of the Department of Urology, the University of California, Davis, Medical Center in Sacramento.
When he was asked to discuss the case against cryosurgery at the Prostate Cancer Shootout II, Dr. deVere White said that at first he had prepared only mild criticism. "One hates to be a naysayer about something that is new and not fully tested, so I came here prepared to say we need to pursue it." However, data reported by Jeffrey K. Cohen, MD, who spoke in favor of cryoablation, convinced him that cryotherapy is "dead."
Dr. Cohen's data showed that for men with a Gleason score of 6, PSA level below 10 ng/mL, and clinical grade of T2a, cryosurgery achieves a 60% cure rate. "When you go from an 85% to 90% cure rate for radical prostatectomy 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 the Health Sciences, Pennsylvania, said that cryo-surgery is not his first choice for men in the favorable prostate cancer population. "For a man under the age of 65 with localized disease, radical prostatectomy is at 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 men with unfavorable prostate cancer presentations, such as those who have extrapros-tatic disease; those in their mid-50s who failed radiotherapy; or those who are not candidates for radiotherapy because of previous radiotherapy for rectal cancer, pelvic trauma, or kidney transplantation.
Dr. Cohen acknowledged that the first 100 patients he treated with cryosurgery tended to have high rates of biopsy failure; the overall positive biopsy rate 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, which indicates how results improve with expertise.
Nevertheless, a 60% biochemical cure rate (PSA level of 0.4 ng/mL or less) at six years is the "best we can do" with cryosurgery for men with favorable presentations of prostate cancer, Dr. Cohen said.
In the unfavorable group, one third of patients had PSA of 0.4 ng/mL or less at two years. These figures nevertheless stand up well in comparison with the results of treatment with external beam radiotherapy, Dr. Cohen said.
Cryosurgery performed better than external beam radiotherapy for men in the unfavorable population in a recent study at Allegheny General Hospital (Urology 45:624-663, 1995), he said. External beam radiotherapy in that study had a 51% positive biopsy rate in the first three years after treatment versus 28% for cryosurgery.
As Salvage After Radiotherapy
Cryosurgery also may be tried in men in the unfavorable group whose cancer persists after radiotherapy, Dr. Cohen suggested. "These men represent a special challenge, because they weren't good candidates for treatment 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 "not good but not bad," he said.
Dr. Cohen continues to test this form of therapy because he believes it is as good as or better than external beam radiation for men with advanced prostate cancer. "The results are good for stage C or higher prostate cancer, and the quality of life is about the same. That is why we persist," Dr. Cohen concluded.