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

To evaluate iceball margins after magnetic resonance (MR)-guided focal salvage prostate cryoablation and determine the correlation with local outcome.

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.

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 < .001).

Iceball margins appear to correlate with local outcome following MR-guided focal salvage prostate cryoablation. Our initial data suggest that freezing should be applied at minimum 5 mm beyond the border of an MR-visible recurrent prostate tumour for successful ablation, with a wider margin appearing desirable.

• Shortest iceball margin most often occurred in anteroposterior direction • Margins were smaller in tumours that were larger or posteriorly located • Minimum iceball margin was a predictor of early local tumour progression • A minimum 5-mm margin seems required for effective cryoablation of recurrent PCa.

European radiology. 2017 Apr 13 [Epub ahead of print]

Christiaan G Overduin, Sjoerd F M Jenniskens, J P Michiel Sedelaar, Joyce G R Bomers, Jurgen J Fütterer

Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101 (767), 6500 HB, Nijmegen, The Netherlands. ., Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101 (767), 6500 HB, Nijmegen, The Netherlands., Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands.