Magnetic Resonance Imaging in Active Surveillance for Prostate Cancer

Introduction Prostate MRI is increasingly used to identify suitable candidates for active surveillance (AS) and allows patients with low- or intermediate-risk prostate cancer to be monitored safely and treated promptly if disease progression occurs. This thesis examines the literature and generates new insights into the evolving role of MRI in AS. Methods I conducted a narrative review synthesising current evidence on the use of MRI in AS. I updated the PRECISE recommendations for reporting serial MRI scans following an expert consensus meeting to address some of the prior limitations and improve standardisation. I collated and analysed clinical data from 1,150 patients in the University College London Hospitals (UCLH) AS cohort, to assess the effectiveness of REASSURE, a risk-adapted, MRI-led AS approach. I then compared REASSURE to other risk-adapted and protocol-based AS strategies. I also completed a multicentre study investigating the inter- and intra-rater reliability of MRI-based prostate cancer lesion size measurements. Results The updated PRECISE v2 recommendations proposed the clarification of stable disease as either visible or non-visible. In the UCLH REASSURE cohort, despite a higher baseline risk profile than most AS cohorts, favourable long-term clinical outcomes were observed with 67/1,150 patients upgraded to Gleason 4+3 over a median follow-up greater than five years. REASSURE outperformed other AS protocols in risk-stratifying patients at baseline to predict event-free survival and reduced the number of MRIs and biopsies required. I found substantial variability in MRI lesion size measurements between different radiologists and even the same radiologist during different reading sessions, challenging its reliability as a standalone marker and underscoring the need for further research on this topic. Conclusions MRI-led, risk-adapted AS represents a safe, efficient, and patient-centred alternative to traditional prostate biopsy-intensive protocols. This thesis supports its broader clinical implementation and identifies future research priorities for the use of MRI in AS.