Definition of biochemical success following primary whole gland prostate cryoablation

Abstract

Purpose: We identified an evidence-based definition of biochemical success following primary whole gland prostate cryoablation.

Materials and methods: The COLD Registry was queried for a risk stratified cohort of otherwise treatment naïve patients who underwent primary whole gland prostate cryoablation, of whom none had received any type of adjuvant therapy. Minimum followup in all study patients was 5 years. Variables included patient age, prostate specific antigen at diagnosis, Gleason score, D'Amico risk category and followup prostate specific antigen. Biochemical progression-free survival was studied based on Kaplan-Meier results using the Phoenix definition. HRs were calculated using proc PHReg.

Results: Of 1,111 patients 891 achieved nadir prostate specific antigen less than 0.4 ng/ml, which correlated with a 5-year biochemical progression-free survival rate of 90.4% in those at low risk, 81.1% in those at intermediate risk and 73.6% in those at high risk. Nadir prostate specific antigen 0.4 ng/ml or greater was associated with 24-month biochemical failure of 29.2% in those at low risk, 46.4% in those at intermediate risk and 48.9% in those at high risk. Statistical analysis failed to reveal a superior prostate specific antigen end point compared to 0.4 ng/ml. HR findings supported the relevance of the end point of less than 0.4 ng/ml (p <0.0001).

Conclusions: To our knowledge this study represents the first evidence-based definition of biochemical success after primary whole gland prostate cryoablation. Nadir prostate specific antigen less than 0.4 ng/ml was the best objective indicator of biochemical success. Nadir prostate specific antigen 0.4 ng/ml or greater was associated with less favorable biochemical progression, precluding the use of a higher nadir prostate specific antigen end point (HR 5.649, 95% CI 4.33-7.38, p <0.0001).

Keywords: cryosurgery; disease progression; mortality; prostate; prostate-specific antigen.