Pathological Findings and Magnetic Resonance Imaging Concordance at Salvage Radical Prostatectomy for Local Recurrence following Partial Ablation Using High Intensity Focused Ultrasound

Purpose: We describe the pathological characteristics of recurrence following high intensity focused ultrasound partial ablation in men treated with salvage robot-assisted radical prostatectomy. We assessed the sensitivity of magnetic resonance imaging before salvage robot-assisted radical prostatectomy in these men.

Materials and methods: A total of 35 men underwent salvage robot-assisted radical prostatectomy after high intensity focused ultrasound partial ablation from 2012 to 2018. We compared clinicopathological characteristics before ultrasound and before salvage prostatectomy after ultrasound to histopathology on salvage prostatectomy. We assessed infield recurrence, out of field disease, positive surgical margins and magnetic resonance imaging sensitivity before salvage robot-assisted radical prostatectomy.

Results: Before high intensity focused ultrasound 55.9% of men had multifocal disease and 47.1% had Gleason 3 + 3 disease outside the treatment field. Median time to salvage prostatectomy was 16 months (IQR 11-26). Indications for salvage prostatectomy were infield recurrence in 55.8% of cases, out of field recurrence in 20.6%, and infield and out of field recurrence in 23.5%. On salvage prostatectomy histopathology revealed significant cancer, defined as ISUP (International Society of Urological Pathology) 2 or greater, infield in 97.1% of cases, out of field in 81.3%, and infield and out of field in 79.4%. Of the cases 82.4% were adversely reclassified at salvage prostatectomy compared to 67.6% before ultrasound. The positive surgical margin rate was 40.0%. Of the positive margins 84.6% were in the region of previous ultrasound despite wide excision, including pT2 in 28.6%, pT3 in 47.6% and size 3 mm or greater, pT3 or multifocal (ie significant) in 31.4%. After ultrasound the sensitivity of magnetic resonance imaging for infield and out of field recurrence was 81.8% and 60.7%, respectively.

Conclusions: Salvage robot-assisted radical prostatectomy may confer a higher risk of positive surgical margins, upgrading and up-staging than primary robot-assisted radical prostatectomy. High intensity focused ultrasound carries a risk of recurrence inside and outside the ablation zone. This information may inform salvage surgical planning and patient counseling regarding the choice of initial therapy and salvage treatment after high intensity focused ultrasound.