Diagnostic Accuracy and Prognostic Value of Serial Prostate Multiparametric Magnetic Resonance Imaging in Men on Active Surveillance for Prostate Cancer

Abstract

Background: Multiparametric magnetic resonance imaging (MRI) is increasingly utilized to improve the detection of clinically significant prostate cancer. Evidence for serial MRI in men on active surveillance (AS) is lacking.

Objective: To evaluate the role of MRI in detecting Gleason grade group (GG) ≥2 disease in confirmatory and subsequent surveillance biopsies for men on AS.

Design, setting, and participants: This was a single-center study of men with low-risk prostate cancer enrolled in an AS cohort between 2006 and 2018. All men were diagnosed by systematic biopsy and underwent MRI prior to confirmatory ("MRI1") and subsequent surveillance ("MRI2") biopsies. MRI lesions were scored with Prostate Imaging Reporting and Data System (PI-RADS) version 2.

Outcome measurements and statistical analysis: The primary outcome was biopsy upgrade to GG ≥ 2 prostate cancer, and the secondary outcome was definitive treatment. Test characteristics for PI-RADS score were calculated. Multivariable logistic and Cox proportional hazard regression models were used to determine the associations between PI-RADS score change and outcomes, on a per-examination basis.

Results and limitations: Of 125 men with a median follow-up of 78 mo, 38% experienced an increase in PI-RADS scores. The sensitivity and positive predictive value of PI-RADS ≥3 for GG ≥ 2 disease improved from MRI1 to MRI2 (from 85% to 91% and from 26% to 49%, respectively). An increase in PI-RADS scores from MRI1 to MRI2 was associated with GG ≥ 2 (odds ratio [OR] 4.8, 95% confidence interval [CI] 1.7-13.2) compared with PI-RADS 1-3 on both MRI scans. Men with PI-RADS 4-5 lesions on both MRI scans had a higher likelihood of GG ≥ 2 than patients with PI-RADS 1-3 lesions on both (OR 3.3, 95% CI 1.3-8.6). Importantly, any increase in PI-RADS scores was independently associated with definitive treatment (hazard ratio 3.9, 95% CI 1.3-11.9). This study was limited by its retrospective, single-center design.

Conclusions: The prognostic value of MRI improves with serial examination and provides additional risk stratification. Validation in other cohorts is needed.

Patient summary: We looked at the role of serial prostate magnetic resonance imaging in men with low-risk prostate cancer on active surveillance at the University of California, San Francisco. We found that both consistently visible and increasingly suspicious lesions were associated with biopsy upgrade and definitive treatment.

Keywords: Active surveillance; Confirmatory biopsy; Multiparametric magnetic resonance imaging; Outcome research; Prostate cancer; Surveillance biopsy.