Magnetic resonance imaging (MRI)-led active surveillance (AS) for prostate cancer uses prostate-specific antigen (PSA) and MRI for regular monitoring with biopsy only when indicated by changes in MRI or PSA density.

This clinical cohort, which started AS between February 2000 and July 2023, includes those with (1) Gleason score (GS) ≤3 + 4, (2) PSA <20 ng/ml, and (3) at least two MRI scans. The primary outcome was event-free survival (EFS) defined as histological upgrade to GS ≥4 + 3 or transition to treatment. Patients were risk stratified by baseline MRI visibility and Gleason pattern 4, and Kaplan-Meier curves were used to compare groups.

The cohort consisted of 1150 patients with a median follow-up of 64 mo per person overall (quartiles: 32, 107). At baseline, of these 1150 patients, 412 (36%) had GS 3 + 4, 627 (55%) had an MRI-visible lesion, and 201 (17%) had MRI-visible Gleason 3 + 4 disease. The EFS rate at 5 yr was 91% (95% confidence interval: 88-94%) for nonvisible GS 3 + 3, 71% (65-78%) for MRI-visible GS 3 + 3, 70% (63-78%) for nonvisible GS 3 + 4, and 44% (35-54%) for MRI-visible GS 3 + 4. A total of 487 patients had follow-up biopsies, with 74 having more than one, and histological upgrade to GS ≥4 + 3 was uncommon, occurring in 67 patients. Progression to nodal or bone metastases occurred in ten patients and only in those who had declined the recommended follow-up MRI and/or biopsies. Thirty patients chose treatment despite having stable characteristics, and 31 were lost to follow-up.

MRI visibility and secondary Gleason pattern 4 at baseline are associated with progression to treatment and to primary Gleason pattern 4 during MRI-led AS.