Background and objectives: Salvage prostate cryoablation is an effective treatment for patients with localized prostate cancer relapse following primary radiotherapy. The postsalvage prostate-specific antigen (PSA) nadir that best predicts long-term biochemical progression-free survival (bPFS) is not yet defined. We sought to determine what nadir PSA best predicted success following salvage whole-gland cryoablation.
Patients and methods: We retrospectively reviewed a cohort of 486 hormone-naive patients who underwent salvage whole-gland cryoablation from the Cryo On-Line Database (COLD). Studied variables were age, race, initial PSA, presalvage prostate-specific antigen (psPSA), initial Gleason score, Gleason score at presalvage biopsy, clinical stage, and follow-up PSA values. Kaplan-Meier (KM) analysis was used to calculate 5-year bPFS using the Phoenix criteria. Hazard ratio and relative risk were also analyzed. Differences among the KM estimates, at 5 years, were calculated using the log-rank test.
Results: Using group thresholds, KM analysis identified nadir PSA less than or greater than 0.4 ng/mL as the nadir PSA threshold, with the greatest difference in bPFS. The KM estimated 5-year bPFS was 75.5% and 22.1% for nadir PSA <0.4 and ≥0.4 ng/mL, respectively. Stratified by psPSA, the KM estimated 5-year bPFS comparing patients with PSA nadir <0.4 vs ≥0.4 ng/mL was 78.5% and 17.9% (p < 0.0001) for psPSA <4 ng/mL, 77.1% and 15.7% (p < 0.0001) for psPSA 4-10 ng/mL, and 77.8% and 16.8% (p < 0.0001) for psPSA >10 ng/mL, respectively.
Conclusion: The best objective indicator of biochemical success following whole-gland salvage cryoablation of the prostate is PSA nadir <0.4 ng/mL.