MRI Monitoring for Focal Ablation Series
James Nie, BS, Soum Lokeshwar, MD-MBA, Daniel Segal, MD, Ghazal Khajir, MD, Benjamin Press, MD, Preston Sprenkle, MD.
Yale School of Medicine, NEW HAVEN, CT, USA.
BACKGROUND: We report the utility of MRI-based follow-up and short-term outcomes of primary focal ablation for localized low-risk prostate cancer (PCa).
METHODS: We conducted retrospective analysis of 19 men who underwent focal targeted cryoablation (n=16) or Nanoknife electroporation (n=3) from 2014-20. MRI-US fusion biopsy (FBx) and systematic core needle biopsy were conducted at 6 and 24 months. Clinically significant PCa was defined as >GG2. Biochemical recurrence was defined by Phoenix criteria. Treatment failure was defined by radical prostatectomy (RP), radiation therapy, or repeat ablation.
RESULTS: Median age, PSA, and prostate volume at ablation were 64 years, 8.2ng/mL, and 53cc. Pre-ablation highest grade was grade group 1 (GG1) in 4 men, GG2 in 10, and GG3 in 5. Median follow up was 25.5 months.Two weeks after ablation, 1 high-risk patient (PSA>20) exhibited residual PIRADs-5 lesion and underwent RP. 16 patients underwent 6-month FBx (median: 6.9 months). On MRI, no suspicious lesions were visualized in the ablation zone, but 1/16 (6.3%) patients had GG4 disease in the ablation cavity. 2/16 (12.5%) patients developed contralateral (CL) MRI-visible lesions, but no corresponding csPCa on Fbx.10 patients had second Fbx (median: 24.1 months). 1 patient (10%) exhibited a PIRADs-4 lesion in the ablation zone but no csPCa. 1 patient (10%) had two CL PIRADs-4 lesions without corresponding csPCa, but had an un-visualized ipsilateral GG2cancer. 2 additional patients had un-visualized cancers: 1 (10%) with GG2 in the ablation zone and 1 (10%) with an ipsilateral GG2 cancer. 3 patients underwent RP, 2 radiation, and 1 ablation for CL recurrence. Mean pre-ablation PSAD for patients with treatment failure was 0.24, compared to 0.17 for those without. No new or worsening urinary incontinence occurred, but 4/19 patients had new/worsening erectile dysfunction. 1/19 patients were lost to follow[NJ1] up, but all other patients without treatment failure continue on PSA surveillance without evidence of BCR.
CONCLUSIONS: For primary focal ablation, MRI based monitoring alone may be insufficient for monitoring disease recurrence. None of the 4 patients with csPCa detected on biopsy had corresponding lesions detected on MRI. Patients with higher pre-ablation PSAD may be at more risk for treatment failure. We report a 24-month salvage treatment free rate of 68.4%. 
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