RE: Prevalence of MRI Lesions in Men Responding to a GP-Led Invitation for a Prostate Health Check: A Prospective Cohort Study

Abstract

Controversy surrounds population-based screening for prostate cancer, which has typically relied on PSA level for risk stratification. This commentary examines the recent prospective trial examining the use of biphasic prostate MRI scans as a screening tool for prostate cancer. Using a reliable test, such as MRI prostate, at an earlier point along the diagnostic pathway, the authors provide a novel solution to a difficult problem. Further research is warranted to assess how biphasic MRI might be feasible at a population level.

This was a prospective cohort study to assess the use of an MRI-led approach to prostate cancer screening [1]. Men aged 50–75 were invited to participate in an MRI screening and PSA testing from participating GP practices. Men underwent a 10-min, non-contrast, biphasic MRI prostate including a T2-weighted sequence and diffusion-weighted imaging using a high b value of 2000 s/mm² and a PSA test. The MRI outcome was a binary positive or negative result as read by two radiologists independently. Men were screen positive if they had a positive MRI scan or a PSA density of >0.12 ng/mL. Screen-positive men were referred for standard NHS assessment, involving mpMRI scanning and targeted biopsies. Clinically significant prostate cancer was defined as Gleason pattern 4 or above.

Of the 2096 screened patients, 303 men completed screening MRI and PSA testing. A total of 48 men, or 16%, had a positive screening MRI, and an additional 5% had a raised PSA density alone. After NHS assessment, 29 men (9.6%) of men were diagnosed with clinically significant prostate cancer, and 3 men (1%) had clinically insignificant prostate cancer. Of note, two out of three men with a positive MRI and half of men with clinically significant prostate cancer had a PSA < 3 ng/mL.

There remains ongoing controversy surrounding population-based screening for prostate cancer. Whilst there is evidence that population-based screening leads to an increased detection of prostate cancer, PSA-led population screening programs have traditionally over-detected clinically insignificant prostate cancer and increased treatment-associated morbidity. A 2018 Cochrane systematic review and meta-analysis comprising 721,718 patients found that at best, PSA-led population screening may have a small effect on prostate-specific mortality; however, it comes at a cost of significant morbidity to men who have over-treatment [2]. Currently, Lithuania is the only country in the world to use a population-based PSA screening program.

Current early detection of prostate cancer recommends taking an individualized approach to PSA testing. In those deemed high risk based on elevated PSA, multiparametric MRI is now widely used as a triage tool for the detection of clinically significant prostate cancer, and it has led to approximately one in four men avoiding an unnecessary prostate biopsy.

This study examines how bringing biphasic MRI forward in the algorithm of prostate cancer diagnosis to the screening stage may improve the diagnosis of significant prostate cancer, potentially leading to an improvement in population-based survival.

The advantages of the MRI used in this study include the limited time needed for the acquisition of images, the ability to avoid contrast, and the ease of interpretation, with a clear, binary outcome. These advantages are becoming increasingly important in a time of limited resources, particularly considering the time and cost of these scans and its applicability to population-based screening.

In this study, the use of MRI alone was reasonably good, detecting clinically significant prostate cancer, with a low risk of detecting clinically insignificant prostate cancer and reducing the morbidity of detection. However, the findings suggest that we cannot do away completely with PSA. There were four patients with clinically significant prostate cancer who had a negative MRI but positive PSA. Conversely, a number of men had a positive MRI with a low PSA yet still had clinically significant cancer. This suggests that from a screening point of view, biphasic MRI and PSA would still need to be used in conjunction with one another.

A limitation of this study was the low participation by black men. Black men were less likely to participate, despite this group being at higher risk of developing clinically significant prostate cancer. We commend the authors on identifying novel ways to improve outreach to this at-risk group, with future studies looking to use a mobile-MRI van to improve participation [3].

This study represents an innovative way of using a well-known tool to help improve the detection of clinically significant prostate cancer at a population level.