Multiparametric Magnetic Resonance Imaging for Active Surveillance of Prostate Cancer

Abstract

Active surveillance has gained popularity as anacceptable management option for men with low-riskprostate cancer. Successful utilization of this strategycan delay or prevent unnecessary interventions - therebyreducing morbidity associated with overtreatment. Theusefulness of active surveillance primarily depends oncorrect identification of patients with low-risk disease.However, current population-wide algorithms and toolsdo not adequately exclude high-risk disease, therebylimiting the confidence of clinicians and patients togo on active surveillance. Novel imaging tools suchas mpMRI provide information about the size andlocation of potential cancers enabling more informedtreatment decisions. The term "multiparametric" inprostate mpMRI refers to the summation of severalMRI series into one examination whose initial goalis to identify potential clinically-significant lesionssuitable for targeted biopsy. The main advantages ofMRI are its superior anatomic resolution and the lackof ionizing radiation. Recently, the Prostate ImagingReportingand Data System has been instituted as aninternational standard for unifying mpMRI results.The imaging sequences in mpMRI defined by ProstateImaging Reporting and Data System version 2 includes:T2-weighted MRI, diffusion-weighted MRI, derivedapparent-diffusion coefficient from diffusion-weightedMRI, and dynamic contrast-enhanced MRI. The useof mpMRI prior to starting active surveillance couldprevent those with missed, high-grade lesions fromgoing on active surveillance, and reassure those withminimal disease who may be hesitant to take part inactive surveillance. Although larger validation studiesare still necessary, preliminary results suggest mpMRIhas a role in selecting patients for active surveillance.Less certain is the role of mpMRI in monitoring patientson active surveillance, as data on this will take a longtime to mature. The biggest obstacles to routine use ofprostate MRI are quality control, cost, reproducibility,and access. Nevertheless, there is great a potential formpMRI to improve outcomes and quality of treatment.The major roles of MRI will continue to expand and itsemerging use in standard of care approaches becomesmore clearly defined and supported by increasing levelsof data.