Impact of Cryoprobe Density on Hemigland Ablation Prostate-Specific Antigen Outcomes

Purpose: Prostate-specific antigen (PSA) value interpretation following primary focal cryotherapy (PFC) for prostate cancer remains a challenge. The purpose of this study is to determine significance of cryoprobe density (CPD), defined as number of cryoprobes divided by preoperative prostate volume (mL), on PSA following PFC.Materials and Methods: A total of 109 patients who underwent primary focal therapy with at least 3 follow-ups within a year were included from an Institutional Review Board (IRB)-approved PCa database (IRB No. s18-01661) from July 2010 to October 2019. A Spearman correlation coefficient was used to assess associations between CPD and PSA nadir as well as percent PSA reduction from baseline PSA to posttreatment PSA nadir. We then assessed predictors of a PSA nadir ≥2.0 ng/mL, ≥1.0 ng/mL, as well as biochemical recurrence using multivariate logistic regression model.Results: A total of 109 patients with median follow-up of 78 (60–102) months were included. Median CPD was 0.12 (0.083–0.15). A total of 28 patients (26%) had a PSA nadir ≥2 ng/mL and 60 (55%) had a PSA nadir ≥1.0 ng/mL with median PSA nadir being 1.2 (0.6–2.1) ng/mL. There was a negative correlation between CPD and PSA nadir value (rho=-0.389, p<0.0001). Percent PSA reduction was positively correlated with CPD (rho=0.307, p=0.001). CPD was a significant predictor of PSA nadir value of ≥1.0 ng/mL and ≥2.0 on univariate analysis but not multivariate. CPD was not associated with biochemical recurrence.Conclusion: Results from this study demonstrate a correlation between CPD and PSA outcomes following PFC. Findings from this study may aid in better understanding of the behavior of PSA behavior following PFC.