MP67-08 IDENTIFICATION OF PATIENTS WHO CAN AVOID REPEAT BIOPSY USING MULTIPARAMETRIC MAGNETIC RESONANCE IMAGING

Abstract

INTRODUCTION AND OBJECTIVES: The aim of our study is to determine if multiparametric magnetic resonance imaging (MRI) and/or clinical variables can discriminate between significant cancer and others (indolent or no cancers) before repeat biopsy and to identify men who can avoid repeat biopsy with low risk of missing significant cancer. METHODS: Between 2007 and 2010, 137 consecutive men who underwent repeat biopsy because of elevated or continuous high prostate-specific antigen (PSA) level after initial biopsy (n 1⁄4 88), atypical gland or prostatic intraductal neoplasia at previous biopsy (n 1⁄4 39), positive digital rectal findings (n 1⁄4 1), or patient desire (n 1⁄4 9) were prospectively evaluated. All men underwent 1.5T MRI, including T2-weighted, diffusion-weighted, and/or dynamic contrastenhanced imaging in the prebiopsy setting. Repeat biopsy protocol was 14to 28-core biopsy, including at least 4-core anterior samplings under transrectal ultrasound. Pathological specimens were evaluated according to the 2005 modified Gleason grading. Biopsy results were categorized into biopsy no cancer (BNC), biopsy indolent cancer (BIC), and biopsy significant cancer (BSC). We defined BIC as biopsy GS 3+4, clinical stage T1-T2a based on digital rectal findings (DRE), percent positive core 20%, and maximum cancer length < 5 mm. Cancer other than BIC was defined as BSC. Frequency of biopsy results according to MRI was evaluated. We also assessed clinical variables as predictors for BSC using logistic regression analysis in men with negative MRI. Clinical variables included age, PSA, free PSA, PSA at initial biopsy, rate of increase in PSA, DRE, prostate volume, number of days since initial biopsy, and pathology at previous biopsy. RESULTS: Median age and PSA were 66 years (range: 44e80) and 8.7 ng/ml (range: 1.1e58.6), respectively. The negative and positive MRI group included 84 and 53 men, respectively. The frequency of BNC/BIC/BSC was 76/19/5% in men with negative MRI and 36/19/45% in men with positive MRI. In men with negative MRI, multivariate analysis revealed that DRE was the only significant predictor of BSC. The frequency of BSC in men with negative MRI was 25% (2/8) in abnormal DRE and 3% (2/76) in normal DRE. CONCLUSIONS: Our results suggest that in repeat prostate biopsy setting, men with prebiopsy-negative MRI and normal DRE can avoid biopsy with a very low risk of missing significant cancer.