An evaluation of patient selection criteria on predicting progression-free survival after primary focal unilateral nerve-sparing cryoablation for prostate cancer: recommendations for follow up

Abstract

Purpose: Focal cryoablation targets unilateral disease, sparing healthy tissue and the ipsilateral neurovascular bundle. Given half the prostate is spared, proper patient selection is imperative to optimize outcomes. We report focal cryotherapy outcome data and evaluate the accuracy of the 2007 Task Force patient selection criteria at predicting disease recurrence.

Materials and methods: This is a retrospective patient chart review from a single academic institution. Inclusion criterion is having unilateral prostate cancer treated with primary hemicryoablation. Patients were stratified using the Task Force selection criteria. Exclusion criterion is having had past radiation or hormone therapy. Progression-free survival was calculated using follow-up TRUS biopsy (biopsy done with transrectal ultrasound) and serial prostate-specific antigen (PSA) results (Phoenix criteria). Kaplan-Meier curves were constructed and Cox regression analyses performed, comparing outcomes across patient selection cohorts.

Results: From 2002 to 2009, 77 men underwent primary focal cryosurgery: mean age, 69.5 (SD, 6.7) years; median follow-up time, 24 months (range, 0-87 months); mean precryosurgical PSA, 6.5 (SD, 4.9) ng/mL; median Gleason score, 6 (range, 5-8). There were 44, 31, and 2 men who had D'Amico low-, intermediate-, and high-risk disease, respectively. Seventeen men met Focal Task Force Selection Criteria. After treatment, 22 patients underwent prostate biopsy for suspicion of recurrent disease. Of the 22 patients, 10 (45.5%) had confirmed prostate cancer. Of the 10 patients, 2 had ipsilateral disease, 7 had contralateral disease, and 1 had bilateral disease. Overall biochemical and pathological progression-free survival rates were 72.7% and 87%. The cumulative incidence of biochemical disease progression, using the Kaplan-Meier method, was greater than 75% at 3 years for men with more than 2 positive preoperative biopsy cores and greater than 50% at 5 years for men with 2 or less positive preoperative biopsy cores. No survival differences were seen across cohorts. Pretreatment PSA level, pretreatment Gleason score, number positive cores, and total tumor length were associated with disease progression.

Conclusions: Focal cryotherapy is a promising option for carefully selected patients, although optimization of inclusion criteria is required. Current selection criteria are associated with cancer-free survival. Given no accurate definitions for biochemical failure after focal cryotherapy exist combined with our high biochemical failure rate, mandating 12-month follow-up TRUS biopsy may improve accurate detection of cancer progression. Further follow up will determine optimal patient selection criteria and follow-up protocols for patients undergoing primary focal unilateral nerve-sparing prostate cancer treatment.