Outcomes comparable for cryo, EBRT in prostate cancer

After nearly 7 years of follow-up, cryoablation appears to be as effective as external beam radiation therapy (EBRT) in the treatment of localized prostate cancer, according to the results of a prospective, randomized trial by researchers at the University of Calgary, Alberta, Canada.

No evidence of disease progression-defined as no biochemical evidence of progression, no radiologic evidence of metastasis, and no need for secondary treatment-is the primary efficacy endpoint for the study that was designed as an equivalence trial in which cryoablation would be determined to be as effective as EBRT (prostate dose of 6,800 to 7,300 cGy) if the outcomes difference between groups is less than 10%.

Researchers had planned to enroll 480 men, but enrollment was terminated prematurely due to slow accrual after 244 patients were randomized. Follow-up is planned for 10 years.

Using the protocol definition of biochemical failure (two consecutive PSA rises, the last being >1.0 ng/mL) and with a median duration of follow-up of 82 months, the rates of no evidence of disease progression in the cryoablation and EBRT groups were 75.7% versus 73.9% at 36 months, 72.7% versus 61.6% at 48 months, and 70.4% versus 58.3% at 60 months. The differences between groups are not statistically significant; however, there is a trend favoring cryoablation over EBRT at 48 months and 60 months, and a statistically significant difference favoring cryoablation over EBRT in the secondary endpoint of persistence of local control at 36 months (negative 10-core transrectal ultrasound-guided biopsy rates, 93.5% vs. 73.3%).

"Controversy continues over what constitutes optimal treatment for localized prostate cancer as there remains a conspicuous lack of randomized trials directly comparing different modalities," said lead author Bryan J. Donnelly, MD. "Our experience with accrual underlines that such head-to-head studies are difficult, but can be done, and the results from this study to date suggest cryoablation and EBRT can be considered similarly effective."