MP67-15 TARGETED MAGNETIC RESONANCE IMAGING/ULTRASOUND FUSION BIOPSY IS A SIGNIFICANTLY BETTER PREDICTOR OF TOTAL PROSTATE CANCER TUMOR VOLUME THAN RANDOM 12-CORE BIOPSY

INTRODUCTION AND OBJECTIVES: Tumor quantification with percent core and/or core length involvement is used to infer burden of disease for patients with prostate cancer (PCa). However, controversy exists regarding tumor quantification in random 12 core biopsies due to discrepancies in lesion targeting and overall needle core lengths obtained. Targeted magnetic resonance imaging/ultrasound (MRI/US) fusion biopsy allows for more optimal lesion targeting and interpretation of this parameter. We aim to correlate highest percentage core involvement and corresponding tumor length for both targeted fusion and random 12 core biopsies with total tumor volume. METHODS: Patients who underwent multiparametric MRI (MP MRI) with targeted MRI/US fusion biopsy at our institution between 2007 and 2013 were reviewed. MRI tumor volumes were calculated in fusion biopsy positive lesions and correlated with the highest percentage core involvement and corresponding tumor length in centimeters, for both targeted fusion biopsy and 12 core biopsy. Bivariate analysis was used to determine the empirical relationship between these variables and the correlative R2 value. RESULTS: 823 patients had MP MRI with MRI/US fusion biopsy, of which 100 patients had MRI tumor volumes quantified. Mean age was 62 years and mean PSA was 5.5ng/ml. For highest percentage core involvement, targeted biopsy showed a positive correlation (R1⁄40.54) whereas 12 core biopsy showed a poor correlation (R1⁄40.004) with total tumor volume (p