BMJ Oncology August 21, 2023

Prevalence of MRI lesions in men responding to a GP-led invitation for a prostate health check: a prospective cohort study (REIMAGINE Prostate Cancer Screening Study)

Caroline M Moore, Elena Frangou, Neil McCartan et al.

Bottom Line

In a prospective community-based screening study, upfront biparametric MRI detected a substantial number of clinically significant prostate cancers in men with normal PSA levels, demonstrating the feasibility of MRI as a primary population screening tool.

Key Findings

1. Among the 2,096 men invited, 457 responded (22%) and 303 successfully completed both the screening MRI and PSA test.

2. A positive screening MRI indicating potential cancer was identified in 48 men (16% of the completed cohort).

3. Notably, 67% (32 of 48) of the men with positive MRI lesions had a PSA level below 3 ng/mL, which is the conventional threshold for triggering further investigation.

4. Following standard clinical assessment, 29 men (9.6% of the cohort) were diagnosed with clinically significant prostate cancer.

5. Over half of the men diagnosed with clinically significant disease (15 of 29; 52%) had a PSA score <3 ng/mL, meaning they would have been missed by traditional PSA-only screening pathways.

6. The screening approach resulted in minimal overdiagnosis, with only 3 men (1%) diagnosed with low-risk, clinically insignificant cancer.

Study Design

Design

Prospective Cohort Study

N/A

Sample

303

Patients

Duration

Cross-sectional

Median

Setting

Single center, UK

Population Men aged 50 to 75 years with no prior prostate cancer diagnosis or treatment, identified through participating general practitioner (GP) practices.

Intervention Screening utilizing an unenhanced biparametric prostate MRI alongside a concurrent Prostate-Specific Antigen (PSA) blood test.

Comparator None (Single-arm screening study)

Outcome Uptake of the screening invitation, the prevalence of MRI lesions, and the subsequent detection rate of clinically significant prostate cancer.

Study Limitations

• The single-center feasibility design and relatively small sample size limit the broad generalizability of the findings.

• The low response rate (22%) to the initial screening invitation introduces the potential for healthy volunteer or selection bias.

• Older white men were overrepresented, while Black men, who carry a significantly higher baseline risk of developing and dying from prostate cancer, were underrepresented.

• As a cross-sectional screening study, it lacks long-term follow-up data to determine if an MRI-led screening strategy ultimately reduces prostate cancer-specific mortality.

Clinical Significance

The REIMAGINE study challenges the current paradigm of using PSA as the sole gatekeeper for prostate cancer evaluation. It provides compelling early evidence that an MRI-led screening approach can identify a high volume of aggressive cancers in men with low PSA scores, while simultaneously maintaining a very low overdiagnosis rate (1%) for indolent cancers. These findings support the progression to larger national trials to validate MRI as a frontline prostate cancer screening tool.

Historical Context

Population screening for prostate cancer has long been highly controversial due to the limitations of Prostate-Specific Antigen (PSA) testing. PSA lacks specificity, leading to a high rate of unnecessary biopsies and the overdiagnosis of indolent cancers, while also missing aggressive tumors in men with naturally low PSA levels. Following landmark diagnostic trials like PROMIS and PRECISION, which established the superiority of multiparametric MRI for guiding biopsies in men with elevated PSA, the REIMAGINE study was launched to answer the next logical question: whether MRI could be moved upstream and utilized as an upfront, independent population screening test in the community.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

How does the mechanism of detecting prostate cancer using Prostate-Specific Antigen (PSA) differ from the detection mechanism of biparametric MRI (bpMRI), and why might a clinically significant cancer present with a normal PSA?

Key Response

PSA is a biomarker produced by normal and neoplastic prostate tissue; elevation is often driven by benign prostatic hyperplasia or inflammation. Poorly differentiated, aggressive tumors may lose the ability to secrete PSA, leading to false negatives. In contrast, bpMRI relies on tissue cellularity (via diffusion-weighted imaging) and anatomical structure (via T2-weighted imaging), allowing it to detect dense, aggressive tumor foci regardless of glandular secretion levels.

Resident

A 55-year-old male requests a screening biparametric MRI instead of a standard PSA test after reading about the REIMAGINE study. How should you counsel him regarding current standards of care versus the study findings?

Key Response

While REIMAGINE demonstrates that upfront MRI can detect clinically significant cancers missed by PSA, current AUA and EAU guidelines still recommend shared decision-making around PSA as the initial screening tool. Upfront MRI is not yet standard due to high costs, limited resource availability, and the risk of overdiagnosis or false positives. Counseling should emphasize that population-level MRI screening remains experimental, and MRI is currently standard practice primarily for risk stratification after an elevated PSA.

Fellow

The REIMAGINE study utilized biparametric MRI (bpMRI) without intravenous contrast instead of multiparametric MRI (mpMRI). What are the specific PI-RADS scoring limitations when omitting dynamic contrast enhancement (DCE), and how might this impact diagnostic confidence in a screening population?

Key Response

bpMRI omits the DCE sequence to save time and avoid gadolinium administration. According to PI-RADS v2.1, DCE serves primarily as a tiebreaker for peripheral zone lesions with a diffusion-weighted imaging (DWI) score of 3, upgrading them to a 4 if focal enhancement is present. Omitting DCE removes this step, which might slightly decrease sensitivity for some equivocal peripheral zone cancers. Fellows must balance the trade-off between the efficiency of bpMRI in screening and the loss of DCE for characterizing indeterminate lesions.

Attending

If upfront MRI becomes the primary population screening tool for prostate cancer, how will this paradigm shift impact healthcare resource allocation, downstream biopsy thresholds, and the management of incidental findings?

Key Response

Adopting MRI as a primary screen shifts the diagnostic bottleneck from laboratory tests to radiology capacity and urology biopsy schedules. While detecting PSA-occult cancers is valuable, population-wide MRI will yield a massive volume of PI-RADS 3 (indeterminate) lesions and incidental findings. Attendings must prepare for the clinical and psychological burden this places on patients, requiring new strategies for triaging lesions, optimizing active surveillance, and managing the strain on the urologic workforce.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The REIMAGINE study utilized a GP-led invitation model with a specific response rate. How might volunteer bias influence the estimated prevalence of MRI lesions, and what specific methodological designs are required for a phase III trial to evaluate true screening efficacy?

Key Response

Men responding to a GP invitation are often more health-conscious or may have unmeasured risk factors like family history, leading to volunteer bias that can skew the prevalence estimates compared to the general population. To definitively prove screening efficacy, a future phase III study must utilize a randomized controlled design comparing upfront MRI against standard PSA screening and no screening, with long-term follow-up powered to assess prostate cancer-specific mortality and quality-adjusted life years rather than just cancer detection rates.

Journal Editor

Men with negative MRIs in the REIMAGINE cohort did not undergo systematic prostate biopsy. How does this lack of verification for test negatives introduce ascertainment bias, and what caveats must be included regarding the reported accuracy metrics?

Key Response

Because ethics and practicality prevent systematic biopsies on asymptomatic men with negative MRIs, the study suffers from partial verification (or workup) bias. The true number of false negatives remains unknown, which artificially inflates the apparent sensitivity and negative predictive value of the bpMRI screening pathway. A rigorous editorial review would require the authors to explicitly state that true diagnostic test accuracy (sensitivity and specificity) cannot be definitively calculated from this cohort due to the unverified negative cases.

Guideline Committee

Based on the REIMAGINE findings, what specific thresholds of evidence must be met before guideline bodies like the EAU or AUA update their recommendations to incorporate upfront bpMRI as a primary prostate cancer screening tool?

Key Response

Current EAU and AUA guidelines strongly endorse PSA as the initial screening test (with shared decision-making) and recommend MRI primarily as a triage tool prior to biopsy for men with elevated PSA. While REIMAGINE provides compelling Level 2/3 evidence for MRI feasibility and cancer detection in normal-PSA men, guideline committees require Level 1 evidence from randomized controlled trials demonstrating that primary MRI screening improves prostate cancer-specific survival and is highly cost-effective before recommending a complete paradigm shift away from PSA-first screening.

Clinical Landscape

Noteworthy Related Trials

2009

ERSPC Trial

n = 162,243 · NEJM

Tested

PSA-based screening for prostate cancer

Population

Men aged 55 to 69 years

Comparator

No screening

Endpoint

Prostate-cancer-specific mortality

Key result: PSA screening reduced prostate cancer mortality by 20 percent but was associated with a high risk of overdiagnosis and overtreatment.

2018

PRECISION Trial

n = 500 · NEJM

Tested

Multiparametric MRI with targeted biopsy

Population

Men with clinical suspicion of prostate cancer without prior biopsy

Comparator

Standard TRUS-guided biopsy

Endpoint

Detection of clinically significant prostate cancer

Key result: The MRI pathway detected significantly more clinically significant cancers and fewer insignificant cancers compared to standard biopsy.

2021

IP1-PROSTAGRAM

n = 408 · JAMA Oncol

Tested

Screening with non-contrast abbreviated MRI

Population

Men aged 50 to 69 years from the general population

Comparator

PSA test

Endpoint

Proportion of men with positive screening results needing biopsy

Key result: MRI screening detected more clinically significant prostate cancers than PSA alone without significantly increasing the detection of insignificant cancers.

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