Predictors of biochemical recurrence after primary focal cryosurgery (hemiablation) for localized prostate cancer: A multi-institutional analytic comparison of Phoenix and Stuttgart criteria

Abstract

Background: The Phoenix definition (PD) and Stuttgart definition (SD) designed to determine biochemical recurrence (BCR) in patients with postradiotherapy and high-intensity focused ultrasound organ-confined prostate cancer are being applied to follow patients after cryosurgery. We sought to identify predictors of BCR using the PD and SD criteria in patients who underwent primary focal cryosurgery (PFC).

Materials and methods: We performed a retrospective review of patients who underwent PFC (hemiablation) at 2 referral centers from 2000 to 2014. Patients were followed up with serial prostate-specific antigen (PSA). PSA levels, pre- and post-PFC biopsy, Gleason scores, number of positive cores, and BCR (PD = [PSA nadir+2ng/ml]; SD = [PSA nadir+1.2ng/ml]) were recorded. Patients who experienced BCR were biopsied, monitored carefully or treated at the discretion of the treating urologist. Cox regression and survival analyses were performed to assess time to BCR using PD and SD.

Results: A total of 163 patients were included with a median follow-up of 36.6 (interquartile range: 18.9-56.4) months. In all, 64 (39.5%) and 98 (60.5%) experienced BCR based on PD and SD, respectively. On multivariable Cox regression, the number of positive pre-PFC biopsy cores was an independent predictor of both PD (hazard ratio [HR] = 1.4, P = 0.001) and SD (HR = 1.3, P = 0.006) BCRs. Post-PFC PSA nadir was an independent predictor of BCR using the PD (HR = 2.2, P = 0.024) but not SD (HR = 1.4, P = 0.181). Survival analysis demonstrated a 3-year BCR-free survival rate of 56% and 36% for PD and SD, respectively. Of those biopsied after BCR, 14/26 (53.8%) using the PD and 18/35 (51.4%) using the SD were found to have residual/recurrent cancer. Of those with prostate cancer on post-PFC biopsy, 57.1% of those with BCR by the PD and 66.7% of those with BCR by the SD were found to have a Gleason score ≥7.

Conclusion: Both the PD and the SD may be used to determine BCR in post-PFC patients. However, the ideal definition of BCR after PFC remains to be elucidated.

Keywords: Biochemical disease-free survival; Phoenix; Primary focal cryosurgery; Prostate cancer; Stuttgart.