Session: MP40: Prostate Cancer: Detection & Screening I
MP40-09: External validation of a Multiparametric Magnetic Resonance Imaging volumetric model to predict the utility of systematic biopsies at the time of targeted biopsy
Introduction: In this study we aimed to externally validate a nomogram based on MRI volumetric parameters and clinical information for deciding when SBx (Standard Biopsy) should be performed in addition to TBx (Target Biopsy)in men with suspicious prostate MRI. Methods: We retrospectevely analysed a prospectevely mantained databes of 496 biopsy naïve men undergoing prostate biopsy with a pre-biopsy multiparametric Magnetic Resonance Imaging (mpMRI) at two institutions. Prostate MRI was performed according to PI-RADS recommendations including T1-wighted (T1WI) and T2-weighted images (T2WI), diffusion weighted images (DWI) with apparent diffusion coefficient (ADC) maps, and dyamic contrast enhances images (DCEI). Men with PIRADSsv 2.1 score of 3-5 were included. All patients underwent MRI-Ultrasound Fusion biopsy of each MRI-suspicious lesion and a fourteen-systematic biopsy according to our protocol. Lesion volume percentage was computed as the ratio of cancer volume on MRI divided the whole prostate volume. Outcomes of this study were non-clinically significant PCa (ncsPCa) (Gleason Grade Group 1) and clinically significant PCa (csPCa) (Gleason Grade Group >1). The model was evaluated with AUC (Area Under the Curve) decision curve analyses and a systematic analysis of model derived probability cut-offs in terms of number of ncsPCa diagnosis avoidance and number of csPCa diagnosed. Results: The nomogram includes age, PSA value, prostate volume, PIRADSsv2.1 score, MRI-suspicion lesion volume percentage, and lesion location. The AUC was 0.73. Using different nomogram cut-offs (from 5% to 30%), 19-58% of men would avoided SBx while missing 0-10% of csPCA and avoiding detection of 6-31% of ncsPCa. These results are similar to those found in the multi-insitutional external validation study based on IMPROD trial (n=122) and MULTI-IMPROD trial (n=262). Decision Curve Analysis (DCA) shows that this nomogram increases the overall net clinical benefit when threshold probability is above 10%. Conclusions: The present study supports the potential utility of a model based on MRI volumetrics for the selection of men with a clinical suspicion of prostate cancer who would benefit of SBx in addition to TBx. SOURCE OF Funding: None
