Is prebiopsy MRI good enough to avoid prostate biopsy? A cohort study over a 1-year period

Abstract

Introduction Prebiopsy multiparametric magnetic resonance imaging (MRI) is increasingly used in clinical practice to detect clinically significant prostate cancer, although its role is controversial. We audited the accuracy of prebiopsy MRI for men clinically suspected to have prostate cancer who underwent initial transrectal ultrasound (TRUS) biopsy at our institution. Patients and Methods All patients who had a prebiopsy prostate MRI and initial TRUS prostate biopsy from January 1, 2013 to December 31, 2013 were included in the study. Prostate MRI was performed using a 1.5-T machine with T2 and diffusion weighted imaging axial phase. TRUS prostate biopsy was performed using a monoplane ultrasound machine. Systematic 12-core prostate biopsies were taken with a Tru-Cut biopsy needle from the apex, middle, and base of the left and right lobe. Results One hundred seventy-three patients met the inclusion criteria; 128 (74.4%) patients had a lesion detected on MRI and 114 (66.3%) patients had a positive biopsy. The sensitivity of MRI for significant prostate cancer on TRUS biopsy of the prostate was 83.5%, specificity was 35.2%, positive predictive value was 55%, and negative predictive value was 68.9%. A positive MRI scan was significantly associated with significant prostate cancer diagnosis, and higher National Comprehensive Cancer Network (NCCN) risk classification (P ≤.001). MRI detected 62 of 63 NCCN high-risk and 18 of 18 Gleason score 8 to 10 cases. Conclusion The sensitivity and specificity of MRI appears insufficient to avoid TRUS biopsy in all men clinically suspected to have prostate cancer. Standardized MRI reporting and robust prospective studies are needed to define the role of prebiopsy MRI in this setting. For patients at risk of complications from biopsy, a negative MRI scan might be used to exclude high-risk disease.