Risk of Clinically Significant Prostate Cancer after a Nonsuspicious Prostate MRI-A Comparison with the General Population

Background: We compare the risk of clinically significant (csPCa; ISUP Grade Group >= 2) and insignificant prostate cancer (isPCa; ISUP Grade Group 1) in men with a nonsuspicious prostate MRI (nMRI; PI-RADS <= 2) with the general population, and assess the value of PSA density (PSAD) in stratification. Methods: In this retrospective population-based cohort study we identified 1,682 50-79-year-old men, who underwent nMRI at HUS (2016-2019). We compared their age-standardized incidence rates (IR) of csPCa and the odds of isPCa to a local age- and sex-matched general population (n = 230,458) during a six-year follow-up. Comparisons were performed by calculating incidence rate ratios (IRR) and ORs with 95% confidence intervals (CI). We repeated the comparison for the 920 men with nMRI and PSAD < 0.15 ng/mL/cm3. Results: Compared with the general population, the IR of csPCa was significantly higher after nMRI [1,852 vs. 552 per 100,000 person-years; IRR 3.4 (95% CI, 2.8-4.1)]. However, the IR was substantially lower if PSAD was low [778 per 100,000 person-years; IRR 1.4 (95% CI, 0.9-2.0)]. ORs for isPCa were 2.4 (95% CI, 1.7-3.5) for all men with nMRI and 5.0 (95% CI, 2.8-9.1) if PSAD was low. Conclusions: Compared with the general population, the risk of csPCa is not negligible after nMRI. However, men with nMRI and PSAD <0.15 ng/mL/cm3 have worse harm-benefit balance than men in the general population. Impact: Prostate biopsies for men with nMRI should be reserved for cases indicated by additional risk stratification.