Source of Funding: This work was supported in part by the National Cancer Institute (R01CA195505), UCLA CTSI (UL1TR000124), the Jean Perkins Foundation, the Kent Kresa Family Foundation, and the Steven C. Gordon Family Foundation. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute or National Institutes of Health. MP14-16 THE CHARACTERISTICS OF PROSTATE CANCER ON FINAL PATHOLOGY IN MEN UNDERGO RADICAL PROSTATECTOMY WITH A NEGATIVE MULTIPARAMETRIC MAGNETIC RESONANCE IMAGING Richard Thompson*, Mustafa Deebajah, Grace Yaguchi, Eric Walton, Mahdi Bazzi, James Peabody, Mani Menon, Shaheen Alanee, Ali Dabaja, Detroit, MI INTRODUCTION AND OBJECTIVES: Despite advancements in radiological imagining of the prostate with Multiparametric (mp)MRI, clinically significant cancer lesions can still be missed. The objective was to characterize the final pathology in men with negative mpMRI findings for PI-RADS 3 or greater but positive findings of prostate adenocarcinoma after prostatectomy. METHODS: An institutional retrospective study of all patients who received a prostate mpMRI for clinical suspicion of prostate cancer from 2015 to 2017 was performed. Patients who had a negative mpMRI for PI-RAD lesions of 3 or greater were identified and of this sub-pop- ulation, patients who underwent a prostatectomy the final pathology were analyzed. RESULTS: 592 men had prostate mpMRI performed between 2015 and 2017, 100 of these men had a prostatectomy. 14 men (9 white, 3 black, 2 other) had negative mpMRI for PIRAD 3 or greater but had a prostatectomy with final pathology positive for prostate adeno- carcinoma. The mean (range) for age, PSA, and PSA density was 60 (40 - 72) years, 6.6 (2.3 - 22) ng/mL and 0.15 (0.07- 0.15) ng/mL/cm2, respectively. On final surgical pathology, 11/14 (79%)men had prostate cancer of Gleason 7 or greater (8 had a Gleason 7 (3+4), 1 had Gleason 7 (4+3), 1 Gleason 8 (4+4), 1 Gleason 9 (3+5). Six men (43%) upgraded on surgical pathology from prostate biopsy pathology, and 6 men had extra prostatic extension including 1 who had seminal vesicle extension. CONCLUSIONS: 79% of men with prostate cancer diagnosis and negative mpMRI had clinically significant prostate cancer on final surgical pathology. Our study underscores the importance of obtaining a prostate biopsy despite negative mpMRI findings in patients with suspicion for prostate cancer. Source of Funding: None MP14-17 ROLE OF MAGNETIC RESONANCE IMAGING IN PREDICTING ADVERSE PATHOLOGY POST-RADICAL PROSTATECTOMY Alp Tuna Beksac*, Ugo Falagario, Shivaram Cumarasamy, Akriti Gupta, Paige Xu, Sonya Prasad, Alberto Martini, Hari Thulasidass, Isuru Jayaratna, Ardeshir Rastinehad, Ash Tewari, New York, NY INTRODUCTION AND OBJECTIVES: Multiparametric mag- netic resonance imaging (mpMRI) has become a valuable tool in diagnosing prostate cancer. However, it’s utility in predicting clinical outcomes has not been well defined. We sought to evaluate the ability of MRI to predict adverse pathology. METHODS: Using our institutional radical prostatectomy (RP) database, we identified 206 patients with preoperative mpMRI. Pa- tients who underwent previous radiotherapy and/or androgen depri- vation therapy were excluded from analysis. Biopsy slides were reread by a dedicated genitourinary pathologist. Baseline clinical and pathological data included age, race, BMI, cT stage, biopsy Gleason Score and % of maximum core involvement, diffusion weighted im- aging (DWI), T2w imaging and PI-RADS score. PI-RADS v2 was used. Adverse pathology was defined as Gleason Group>2, patho- logical stage T3 and/or pN+ disease. Univariate association was analyzed by ANOVA, Kruskal-Wallis H Test/ Mann-Whitney U Test, and chi-square/Fisher 0 s exact tests. Multivariable logistic regression was used to model the log odds of adverse pathology with radio- logical features. RESULTS: In univariate analysis, factors associated with adverse pathology included age (p¼0.02), PSA (p¼0.001), maximum core percentage at biopsy (p¼0.015), clinical T stage (p¼0.005), Gleason score (p<0.001), PI-RADS (p<0.001), T2 (p¼0.003), DWI (p<0.001), mpMRI lesion size (p<0.001) and extracapsular extension (p¼0.003). In a logistic regression model adjusting for age, race, and clinical stage, PSA (p¼0.015), PI-RADS (p¼0.030) and Gleason score (p<0.001) were associated with adverse pathology. Lesions with PI- RADS 5 versus 3 are more likely to have adverse pathology (OR: 8.1, 95% CI: 1.2, 57.5; p¼0.04), but this was not true when compared with PI-RADS 4 (OR: 1.9, 95% CI: 0.8, 4.5, p ¼ 0.12). CONCLUSIONS: PI-RADS score, PSA and biopsy Gleason score are independent predictors for adverse pathology features on prostatectomy specimens. e186 THE JOURNAL OF UROLOGY â Vol. 199, No. 4S, Supplement, Friday, May 18, 2018