Multi-parametric magnetic resonance imaging monitoring patients in active surveillance for prostate cancer: a prospective cohort study

Objectives: To evaluate the use of multi-parametric magnetic resonance imaging (mpMRI) and mpMRI guided biopsies (MRGB) for monitoring an active surveillance (AS) prostate cancer cohort. Materials and methods: One year after initial diagnostic TRUS guided biopsy (TRUS-bx), baseline mpMRI, and enrolment in an AS program patients underwent a one year follow-up comprising the usual TRUS-bx and an mpMRI. Prostate MRI lesions were scored on the five-point PIRADS scale version 2. In cases without TRUS-bx progression, patients with PIRADS 4 or 5 lesions were scheduled for MRGB. Progression in TRUS-bx was defined as Gleason score (Gs) up-grades, >3 tumor positive cores or a maximal cancer core length (MCCL) > 50%. In MRGB, Gs upgrade or a MCCL >= 6 mm Gs 3 + 3 lesions were considered to reflect progression. PSA increase or progression in clinical T-classification alone was not considered clinical progression. Results: 50 patients were included in the study. In total 10 (20%) patients had per definition progression at one year follow-up. Seven patients (7/50 = 14%) had clinical progression based on TRUS-bx. mpMRI identified seven newly emerged PIRADS 4 lesions. Three patients with PIRADS 4 lesions had no sign of TRUS-bx progression, while MRGB revealed significant cancer (Gs 7 (3 + 4) and Gs 8 (3 + 5)). Consequently, seven patients underwent definitive treatment. Of these, six and four had a progression on MRI and TRUS-bx, respectively. Conclusions: Our study suggests that mpMRI is at least equal to TRUS-bx in detecting progression at one year follow-up in prostate cancer patients undergoing active surveillance.