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
Publisher URL: https://link.springer.com/article/10.1007/s00330-017-4833-9
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