1. Magnetic resonance imaging detects significant prostate cancer and could be used to reduce unnecessary biopsies: Initial results from a prospective trial Introduction A major limitation of prostate cancer (PCa) screening with PSA & DRE is their poor combined specificity for significant cancer, resulting in a high rate of unnecessary biopsies and over- detection of insignificant tumours. Conclusions Multi-parametric MRI could be used to improve selection of men for biopsy, reducing unnecessary biopsies and over- detection of insignificant tumours whilst maintaining a low rate of missed significant tumours. Results 100 men were included in the initial analysis, with a median age of 62.4 years and PSA of 6.9. 26% had an abnormal DRE and 32% had a family history of prostate cancer. 36% of men were diagnosed with a significant cancer on biopsy. 67% of men had a positive MRI (PIRADS 3 to 5). On chi square analysis, the sensitivity, negative predictive value, specificity and positive predictive value of a positive MRI for significant cancer was 97%, 97%, 50% and 52%. If biopsy had been deferred in men with a negative MRI (PIRADS 1-2), 33 out of 100 men would have avoided biopsy, while only one significant cancer would not have been diagnosed. On uni-variate logistic regression analysis, the area under the curve (AUC) for predicting significant cancer using MRI was 0.85 (95%CI 0.78 – 0.92). On multivariate analysis, the AUC for a predictive model using age, PSA, family history and DRE was 0.84 (95%CI 0.74 – 0.94); adding MRI to this model improved the AUC to 0.91 (0.85 – 0.97), however numbers were limited and this marginally failed to reach significance at interim analysis (p = 0.08). Methods Men planned for biopsy (for suspected PCa) first underwent T2- weighted, diffusion-weighted and dynamic contrast-enhanced imaging without an endorectal coil, at 1.5 or 3 Tesla (in equal numbers). Two prostate MRI experts used the Prostate Imaging Reporting And Data System (PIRADS) to allocate a score from 1 (very unlikely) to 5 (very likely) for suspicion of significant cancer. Two urologists performed grid-directed, trans-perineal biopsy of 14 or 18 regions (20 - 40 cores) depending on prostate volume, with ultrasound-guided cores from MRI-suspicious areas. Significant cancer was defined as tumour with any of the following: PSA >10; Gleason >/=7 with > 5% grade 4; clinical T- stage >T2a. Chi-square, logistic regression and receiver-operating characteristic (ROC) curve analysis was performed. Acknowledgements – research funding: 1) St Vincent’s Prostate Cancer Centre 2) St Vincent’s Clinic Foundation 3) Royal Australian & New Zealand College of Radiologists Aim/ Hypothesis Our hypothesis was that a negative multi-parametric MRI result reliably excluded significant cancer and could be used to avoid biopsy in selected men. Image 2: An MRI showing a suspicious area in the ….. Which was found to represent significant cancer on biopsy and RP Image 1: Prostate MRI reporting template, with 18 regions defined and scores for each suspicious area Thompson J, Shnier R, Moses D, Brenner P, Delprado W, Hayen A, Stricker P. St Vincents Prostate Cancer Centre and Clinic, Kinghorn Cancer Centre, University of New South Wales, Diagnostic MRI Services Randwick NSW, Spectrum Radiology Randwick NSW, Douglass Hanly Moir Pathology Ryde NSW. No. 168 Posters Proudly Supported by: Image 3: AUCs for a model used to predict significant cancer based on: (A) clinical data alone, and (B) MRI findings plus clinical data