Utility of multiparametric magnetic resonance imaging in the risk stratification of men with Grade Group 1 prostate cancer on active surveillance.

OBJECTIVE: To assess if the adoption of multiparametric magnetic resonance imaging (mpMRI) in active surveillance (AS) has improved the identification of occult higher-grade prostate cancer (PCa). PATIENTS AND METHODS: We retrospectively identified men from the Johns Hopkins AS registry enrolled since 2013 (year of mpMRI adoption) with Grade Group (GG) 1 PCa and who underwent a single mpMRI. Men in this group were dichotomised by the presence (n = 207) or absence (negative mpMRI, n = 225) of one or more lesions with a Prostate Imaging-Reporting and Data System (PI-RADS) score of >/= 3. Both groups were compared to a third cohort of men with GG1 PCa enrolled in AS prior to 2013 (pre-mpMRI era, n = 669). The risk of upgrading to GG >/= 2 PCa on follow-up biopsies (performed with or without MRI targeting) was evaluated among the groups using survival analysis. RESULTS: Men in both mpMRI groups underwent a median (interquartile range [IQR]) of 2 (2-3) biopsies separated by a median (IQR) interval of 13 (12-16) months, whereas men in the pre-MRI era underwent a median (IQR) of 3 (2-5) biopsies, separated by a median (IQR) interval of 12 (12-14) months. The 2- and 4-year upgrade-free survival rates were 93% and 83%, 74% and 59%; and, 87% and 76% for the negative mpMRI, PI-RADS >/= 3, and pre-mpMRI-era groups, respectively (P /= 3 group: HR 1.96, 95% CI 1.36-2.82, P < 0.001). CONCLUSIONS: mpMRI improves the risk stratification of men on AS and should be used to aid enrolment and monitoring decisions.