1468 POTENTIAL OF PREBIOPSY MULTIPARAMETRIC MAGNETIC RESONANCE IMAGING TO REDUCE INITIAL BIOPSIES IN MEN WITH SUSPECTED CLINICALLY LOCALIZED PROSTATE CANCER

Abstract

INTRODUCTION AND OBJECTIVES: The aim of our study is to determine whether multiparametric magnetic resonance imaging (MRI) and/or clinical variables can discriminate between significant cancers and the others (indolent or no cancers) before initial biopsy and to identify men who could omit initial biopsy with low risk of missing significant cancer. METHODS: Between 2006 and 2010, 351 consecutive men with prostate-specific antigen (PSA) between 2.5-20 ng/ml and/or digital rectal examination (DRE) suspicious for clinically localized disease were prospectively evaluated. All men underwent a 1.5T MRI, including T2-weighted, diffusion-weighted and/or dynamic contrast-enhanced imaging, and then an initial 14-29 core prostate biopsy including 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, percent positive core / 20% and maximum cancer length 5 mm. Cancer other than BIC was defined as BSC. Overall cohort was divided into low-risk (PSA 10 ng/ml and normal DRE) and high-risk group (PSA / 10 ng/ml and/or abnormal DRE). MRI positive rates and frequency of biopsy results according to MRI were evaluated in these two subgroups. We assessed standard clinical variables as predictors for BSC using logistic regression analysis in men with negative MRI and determined the groups of men with low frequency of BSC. RESULTS: Median age and PSA were 65 years and 6.3 ng/ml, respectively. Highand low-risk group included 106 and 245 men, respectively. Positive MRI rates in high and low risk group were 59% and 38%, respectively (p 0.001). In high-risk group, frequency of BNC/BIC/BSC were 24/8/68% in men with positive MRI and 47/9/44% in men with negative MRI. Frequency of BSC was high regardless of MRI. In low-risk group, frequency of BNC/BIC/BSC were 44/14/43% in men with positive MRI and 77/13/ 9% in men with negative MRI. Frequency of BSC was high in men with positive MRI, while it was low in men with negative MRI. In men with negative MRI in low-risk group, multivariate analysis revealed that prostate volume was the only significant predictor of BSC. Frequency of BSC was 17/7/0% in prostate volume of 30/30-50/ 50 ml, respectively. CONCLUSIONS: Potential ability of MRI to reduce initial biopsies was high in men with PSA 10 ng/ml and normal DRE, while it was limited in men with PSA / 10 ng/ml and/or abnormal DRE.