Introduction: For the last 10-years we employed MR/US Fusion Ablation (MRFA) for the treatment of clinically localized prostate cancer in the office setting. In this study we evaluated the impact of the piRADS 2.1 system on MRI imaging acquired 1-Year after MRFA, with either Cryotherapy or Laser. Methods: Our MRFA protocol registered at NCT02381990 - clinicaltrials.gov - was designed as a longitudinal registry of treatment outcomes after MRFA of cancer lesions. Whilst the protocol was originally designed for Cryotherapy, other ablative energies are emerging and incorporated into the MRFA registry. A total of 1,046 men underwent MRFA for targeted lesions representing <40% of prostate in the office setting between August of 2013 and September 2022. 289 MRFA performed in the last 12 months were excluded. A mpMRI was recommended for all patients at a 1 year follow up mark. For the untreated prostate tissue, the mpMRI - T2, DWI, ADC and DCE images were evaluated and scored according to the piRADS-2.1 system. For the treated areas, success was determined by lack of DCE enhancement. A Transperineal Fusion Biopsy (TPFBx) was recommended all. We evaluated the correlation between the piRADS scores and biopsy pathology. Parametric and non-parametric statistics were performed. Signi?cance level was determined by a p<0.05 Results: Of the 717 eligible patients, 513 underwent a 1-Year MRI assessment and 454 underwent a Transperineal Fusion Biopsy (TPFBx). The were no statistical differences in Clinical Stage, Gleason Grade Groups, PSA distributions and Age between those without without a 1yr TPFBx. Of the 172 men with a positive biopsy, 91 were clinically significant prostate cancers. 57/172 were infield (within 5 mm of treatment margin). The reminder 115 (67%) either de-novo tumors or tumors not diagnosed on their initial biopsy. The piRADS system performed well indicating the presence of cancer as piRADS 1-2, 3, and 4-5 lesions carried cancer detection rates of 5% (8/163), 44% (79/181) and 77% (85/110), respectively (p=0.01). The Figure shows the Gleason Grade Groups (GG) distribution by piRADS Conclusions: This data suggests that piRads V2.1 can be applied to untreated prostate after partial gland ablation. Moreover, if these findings are corroborated, 1yr TPFBx could be avoided on 1yr mpMRI without piRADS 3 to 5 lesions. SOURCE OF Funding: UROLOGICAL RESEARCH NETWORK FOUNDATION
