Percutaneous MR-guided focal cryoablation for recurrent prostate cancer following radiation therapy: retrospective analysis of iceball margins and outcomes

Abstract

Objectives: To evaluate iceball margins after magnetic resonance (MR)-guided focal salvage prostate cryoablation and determine the correlation with local outcome. Methods: A retrospective review was performed on 47 patients that underwent percutaneous MR-guided focal cryoablation for biopsy-proven locally recurrent prostate cancer after primary radiotherapy. Preprocedural diagnostic and intraprocedural MR images were analysed to derive three-directional iceball margins. Local tumour progression after cryoablation was defined as evident tumour recurrence on follow-up MRI, positive MR-guided biopsy or biochemical failure without radiological evidence of metastatic disease. Results: Mean iceball margins were 8.9 mm (range −7.1 to 16.2), 10.1 mm (range 1.1–20.3) and 12.5 mm (range −1.5 to 22.2) in anteroposterior, left–right and craniocaudal direction respectively. Iceball margins were significantly smaller for tumours that were larger (P =.008) or located in the posterior gland (P =.047). Significantly improved local progression-free survival at 1 year post focal cryoablation was seen between patients with iceball margin >10 mm (100%), 5–10 mm (84%) and <5 mm (15%) (P