How Often Does Magnetic Resonance Imaging Detect Prostate Cancer Missed by Transrectal Ultrasound?

Background: Lesion-targeted prostate biopsy based on multiparametric magnetic resonance imaging (mpMRI) has been shown to be superior to systematic transrectal ultrasound (TRUS) biopsy (SBx) alone in men at risk for prostate cancer (PCa). However, the incremental benefit of MRI-targeted biopsy (MBx) beyond SBx with ultrasound-targeted biopsy (UBx) is less clear.

Objective: We performed a three-way comparison of UBx versus MBx versus SBx for PCa detection.

Design, Setting, And Participants: A prospective, single-center cohort study was conducted on consecutive patients with PCa suspicion or low-risk PCa on active surveillance (AS). All men had at least one lesion (Prostate Imaging Reporting and Data System [PI-RADS] ≥3) on pre-biopsy mpMRI. UBx, MBx, and SBx were performed during the same encounter, and the urologists were blinded to MRI results and targeting until both SBx and UBx were completed.

Outcome Measurements And Statistical Analysis: The ability of each biopsy type to identify the highest grade group (GG) was determined, and UBx and MBx were compared using a paired t test.

Results And Limitations: We prospectively enrolled 201 consecutive men undergoing targeted prostate biopsy: 72 (36%) were biopsy-naïve, 34 (17%) had a prior negative SBx, and 95 (47%) were on AS. Median age and prostate-specific antigen were 66 yr (interquartile range [IQR] 62-71) and 6.8 ng/ml (IQR 4.9-9.8), respectively. Suspicious hypoechoic lesions were reported on TRUS in 69%. Among the 169 men with PCa, SBx detected the highest GG or was equivalent to UBx/MBx in 136 (80%) men. UBx detected the highest GG or was equivalent to MBx in 19 (11%) men, and MBx alone detected the highest GG in 14 (8%) men. There was no significant difference between UBx and MBx in direct comparison (p = 0.08). Limitations include that patients were not randomized, our population was heterogeneous, and TRUS expertise at a tertiary care academic center might not reflect routine practice.

Conclusions: In the setting of high expertise and experience with both ultrasound and MRI, MBx offers only a modest benefit over SBx and UBx.

Patient Summary: At a highly experienced academic medical center, we examined the detection rates of prostate cancer among men undergoing prostate biopsy using three techniques: transrectal ultrasound lesion-targeted biopsy, magnetic resonance imaging-targeted biopsy, and systematic biopsy. We identified a few more cases of aggressive prostate cancer with magnetic resonance imaging-targeted biopsy, but a large majority was found by ultrasound alone.