A randomized trial of external beam radiotherapy versus cryoablation in patients with localized prostate cancer

Localized prostate cancer can be treated several different ways, but head-to-head comparisons of treatments are infrequent. The authors of this report conducted a randomized, unblinded, noninferiority trial to compare cryoablation with external beam radiotherapy in these patients.

From December 1997 through February 2003, 244 men with newly diagnosed localized prostate cancer were assigned randomly to receive either cryoablation or radiotherapy (122 men in each arm). All received neoadjuvant antiandrogen therapy. The primary endpoint was disease progression at 36 months based on a trifecta definition: 1) radiologic evidence of metastatic disease, or 2) initiation of further antineoplastic therapy, or 3) biochemical failure. Two definitions of biochemical failure were used: 1) 2 consecutive rises in prostate-specific antigen (PSA) with a final value >1.0 ng/mL, and 2) a rise above PSA nadir + 2 ng/mL. Secondary endpoints included overall survival, disease-specific survival, and prostate biopsy at 36 months.

The median follow-up was 100 months. Disease progression at 36 months was observed in 23.9% (PSA nadir + 2 ng/mL, 17.1%) of men in the cryoablation arm and in 23.7% (PSA nadir + 2 ng/mL, 13.2%) of men in the radiotherapy arm. No difference in overall or disease-specific survival were observed. At 36 months, more patients in the radiotherapy arm had a cancer-positive biopsy (28.9%) compared with patients in the cryoablation arm (7.7%).

The observed difference in disease progression at 36 months was small, 0.2%; however, because of the wide confidence interval, from -10.8% to 11.2%, it was not possible to rule out inferiority (defined a priori as a 10% difference). With longer term follow-up, the trend favors cryoablation. Significantly fewer positive biopsies were documented after cryoablation than after radiotherapy.