Full, partial cryoablation: Good 5-year outcomes

September 1, 2009

Two large studies of cryoablation for prostate cancer showed positive disease-free rates.

Chicago-Two large studies of cryoablation for prostate cancer-one examining full-gland ablation and the other, partial-gland ablation-showed positive disease-free rates at 5 years and 12 months, respectively. Full-gland ablation demonstrated low morbidity, with the exception of erectile dysfunction, while the partial-gland technique provided higher rates of sexual function.

Both studies, presented at the AUA annual meeting, were said to be the largest of their kind to date. Both reported outcomes from the Cryo On Line Database (COLD), a registry that includes data from multiple academic and community centers.

"We report using both of these because currently, there is not a validated definition for chemical failure for cryo. One of the purposes of the COLD registry and one of the primary projects for the coming year will be to look at long-term follow-up data and determine a cryo-specific definition of failure," Dr. Jones said.

The closest researchers have come to a validated definition was in a study led by David Levy, MD, of Cleveland Clinic, said Dr. Jones. That study, also presented here, found that a post-cryotherapy nadir of less than 0.6 ng/mL portends a favorable outcome in 86% of low-risk patients at 5 years.

Focal (or partial) cryoablation targets only identified cancer foci. It is the only form of focal ablation technology approved in the U.S. However, high-intensity focused ultrasound (HIFU) is a focal therapy approved and gaining in popularity in Canada, the United Kingdom, Europe, and parts of Asia.

Nivedita Dhar, MD, assistant professor of urology at the Barbara Ann Karmanos Cancer Institute at Wayne State University, Detroit, presented early results of focal cryotherapy in 795 men. The procedure showed efficacy at 1 year and promising BDFS rates in those men who reached 5-year follow-up, reported Dr. Dhar, who noted that the data comprised the first substantial report on the procedure.

At a median follow-up of 1 year in these patients, positive biopsies were obtained in 36 patients (4.5% of the cohort), three patients (0.4%) had rectal fistula, and incontinence was reported in 11 patients (2.8%).

The BDFS at 5 years, as evaluated by ASTRO criteria, was 81.4% in low-risk patients, 81.2% in intermediate-risk patients, and 83.4% in high-risk patients. However, when the Phoenix criteria were applied, the BDFS rate at 5 years was 63.9% among low-risk patients, 68.7% among intermediate-risk patients, and 40.8% among high-risk patients.

Dr. Dhar told Urology Times that partial cryoablation offered a number of advantages for the patient, among which were low morbidity and much improved rates of sexual function. Approximately 65% of the 134 patients who were potent before the procedure were sexually active 12 months afterward. This is in contrast to the full-gland cryotherapy study, which reported that 181 (33%) of 548 patients who were potent before treatment were sexually active at 12 months afterward.

"The fistula rate is very low now-much lower than it used to be for both full and partial ablation," said Dr. Dhar, who also observed that the improved potency rate seen with focal cryoablation was likely attributable to the technology targeting the tumor while leaving the neurovascular bundle intact.

Both Dr. Dhar and Dr. Jones said that more study is needed and both anticipate that the work will be done. Given the disease and the nature of the technology, Dr. Jones doubted that large, prospective, randomized trials would be conducted.

"The next best option is a large registry database. We have accomplished that," he said. "We are accumulating long-term data on more than 5,000 patients. We have industry support and a mechanism that separates industry from the database through an independent research firm."

Dr. Jones serves as a paid consultant to Endocare, Inc.