Importance
Multiparametric magnetic resonance imaging (MRI), with or without prostate biopsy, has become the standard of care for diagnosing clinically significant prostate cancer. Resource capacity limits widespread adoption. Biparametric MRI, which omits the gadolinium contrast sequence, is a shorter and cheaper alternative offering time-saving capacity gains for health systems globally.
Objective
To assess whether biparametric MRI is noninferior to multiparametric MRI for diagnosis of clinically significant prostate cancer.
Design, Setting, and Participants
A prospective, multicenter, within-patient, noninferiority trial of biopsy-naive men from 22 centers (12 countries) with clinical suspicion of prostate cancer (elevated prostate-specific antigen [PSA] level and/or abnormal digital rectal examination findings) from April 2022 to September 2023, with the last follow-up conducted on December 3, 2024.
Interventions
Participants underwent multiparametric MRI, comprising T2-weighted, diffusion-weighted, and dynamic contrast–enhanced (DCE) sequences. Radiologists reported abbreviated biparametric MRI first (T2-weighted and diffusion-weighted), blinded to the DCE sequence. After unblinding, radiologists reported the full multiparametric MRI. Patients underwent a targeted biopsy with or without systematic biopsy if either biparametric MRI or multiparametric MRI was suggestive of clinically significant prostate cancer.
Main outcomes and measures
The primary outcome was the proportion of men with clinically significant prostate cancer. Secondary outcomes included the proportion of men with clinically insignificant cancer. The noninferiority margin was 5%.
Results
Of 555 men recruited, 490 were included for primary outcome analysis. Median age was 65 (IQR, 59-70) years and median PSA level was 5.6 (IQR, 4.4-8.0) ng/mL. The proportion of patients with abnormal digital rectal examination findings was 12.7%. Biparametric MRI was noninferior to multiparametric MRI, detecting clinically significant prostate cancer in 143 of 490 men (29.2%), compared with 145 of 490 men (29.6%) (difference, −0.4 [95% CI, −1.2 to 0.4] percentage points; P = .50). Biparametric MRI detected clinically insignificant cancer in 45 of 490 men (9.2%), compared with 47 of 490 men (9.6%) with the use of multiparametric MRI (difference, −0.4 [95% CI, −1.2 to 0.4] percentage points). Central quality control demonstrated that 99% of scans were of adequate diagnostic quality.
Conclusion and relevance
In men with suspected prostate cancer, provided image quality is adequate, an abbreviated biparametric MRI scan, with or without targeted biopsy, could become the new standard of care for prostate cancer diagnosis. With approximately 4 million prostate MRIs performed globally annually, adopting biparametric MRI could substantially increase scanner throughput and reduce costs worldwide.
Trial registration
ClinicalTrials.gov Identifier: NCT04571840
Magnetic resonance imaging (MRI) has transformed the diagnostic landscape of prostate cancer. Multiparametric MRI (mpMRI), including T2-weighted, diffusion-weighted, and dynamic contrast-enhanced (DCE) sequences, is now widely adopted as the standard of care. Yet, despite its clinical value, mpMRI poses challenges for health systems: scan times are long, contrast administration requires trained staff, and demand for imaging continues to outstrip capacity worldwide – meaning that not all men receive a pre-biopsy MRI. The PRIME trial, recently published in JAMA, addresses a central question: is biparametric MRI (bpMRI), which omits the contrast sequence, non-inferior to mpMRI for clinically significant cancer detection?
The PRIME trial by Ng & Asif et al., is a prospective, multicentre, within-patient, noninferiority trial conducted across 22 centres in 12 countries. It enrolled 555 biopsy-naïve men with clinical suspicion of prostate cancer, of whom 490 were evaluable. Each participant underwent mpMRI, but images were first reported as bpMRI, blinded to DCE. Biopsies were recommended if either modality suggested clinically significant prostate cancer (csPCa, Gleason grade group ≥2). The primary endpoint was the proportion of men diagnosed with csPCa.
The results were clear: bpMRI was noninferior to mpMRI. Detection rates for csPCa were virtually identical—29.2% with bpMRI and 29.6% with mpMRI (difference –0.4 percentage points). Detection of clinically insignificant disease was similarly comparable (9.2% vs 9.6%, respectively). Importantly, bpMRI achieved equivalent sensitivity and specificity to mpMRI, and did not lead to an increased recommendation for biopsy. What about the value of DCE? In only 6.3% of patients did DCE identify a new or significantly larger suspicious lesion, and in all but two cases, these did not reveal additional csPCa. In terms of downstream clinical impact, DCE sequences altered treatment eligibility in 4.3% and treatment planning in 3.1% of patients. While not negligible, this represents a small minority.
A key strength of PRIME was the rigorous attention to image quality. Before the trial, all participating sites optimised their MRI protocols. Central review confirmed that 99% of scans met adequate diagnostic quality, but in those that did not, the majority of problems arose from the T2-weighted and diffusion-weighted sequences—the very backbone of bpMRI. By contrast, DCE was less often responsible for poor quality. This observation underscores an important point: bpMRI performs well when T2 and DWI are of the highest standard. Whether its noninferiority holds in less optimised or experienced settings remains an open question.
The implications are nonetheless substantial. bpMRI halves scan time, avoids intravenous contrast and associated safety concerns, reduces environmental gadolinium exposure, and eliminates the need for physician presence during scanning. For patients, the exam is shorter and less invasive; for health systems, scanner throughput increases and costs fall. With approximately 4 million prostate MRIs performed annually worldwide, adoption of bpMRI could markedly improve accessibility and efficiency without compromising clinical outcomes.
Of course, caveats must be recognised. PRIME was conducted in expert centres, and successful implementation elsewhere will depend on training and quality assurance. While bpMRI appears sufficient for primary diagnosis, mpMRI may still be valuable in recurrent settings, monitoring, active surveillance, complex staging or problem-solving scenarios.
The PRIME trial provides level 1 evidence that bpMRI can serve as a new first-line standard for prostate cancer diagnosis—but only if imaging quality is assured. Its findings support a paradigm shift: streamlining prostate MRI without losing diagnostic precision.
Furthermore, rather than viewing quality as a limitation, we should view PRIME as proof that high-quality MRI is achievable with small, pragmatic changes. The field must now embrace standardisation and training, ensuring that bpMRI can be delivered reliably across diverse health systems. We should not accept anything less for our patients. For clinical practice guidelines, PRIME offers the strongest rationale yet to reconsider the role of DCE and to embrace bpMRI as a pragmatic, patient-friendly, and resource-efficient alternative.