Separating lethal disease from indolent disease remains the persistent difficulty, and molecular MRI may offer a way to see the difference.
Prostate cancer is the most common cancer in men in 112 countries and accounts for 15% of all male cancer cases, with the caseload growing. The Lancet Commission on Prostate Cancer projects annual new cases will rise from 1.4 million in 2020 to 2.9 million by 2040. More men will be tested, scanned and biopsied each year than ever before. That growth necessitates that the industry improve the way prostate cancer is detected, diagnosed and treated.
Most prostate cancers found through screening will never prove lethal to the men who have them. The UK ProtecT trial, published in the New England Journal of Medicine in 2023, followed 1,643 men with PSA-detected localised disease for a median of 15 years. Prostate cancer killed 2.7% of them, and that figure barely moved whether a man had surgery (2.2%), radiotherapy (2.9%) or active monitoring (3.1%). But some prostate cancers are lethal and need treatment quickly. Telling one from the other at the point of diagnosis remains difficult.
Part of this is a function of how screening works. Slow-growing tumours stay detectable for years, so any screening programme encounters proportionally more of them, while faster-growing cancers move through that detectable window more quickly, a phenomenon known as length-time bias. PSA cannot separate the two on its own. It rises with cancer, but also with age, inflammation and benign enlargement.
So the question facing a clinician is rarely whether there is cancer. It is whether this particular patient’s cancer needs treating, and if so, what kind of treatment?
Current State of Modern Imaging
Over the past decade, three developments have changed how medical imaging can be used for prostate cancer: pre-biopsy MRI, standardised reporting and PSMA-PET.
Pre-biopsy multiparametric MRI (mpMRI) is now recommended in major guidelines before a first biopsy. It combines anatomical T2-weighted imaging with diffusion-weighted sequences and contrast enhancement. Its practical contribution is twofold: men whose scans show nothing suspicious may elect to avoid a biopsy altogether, while those that do have a biopsy will have the biopsy needle directed at a specific portion of the prostate rather than the standard multi-needle sampling of the gland.
The PI-RADS scoring system, now in version 2.1, standardised how radiologists report what they see, on a scale of 1 to 5. It established a method for and common language for radiologists to be more consistent in their reporting. That consistency is important, but it is worth being clear about what PI-RADS does: it standardises the communication of what is considered “suspicious”. It does not include biological or molecular context to the radiological assessment.
While these developments improved how well MRI locates and reports suspicious tissue, they don’t actually change the diagnostic utility of MRI, and still leave a gap for medical imaging to close.
A 2025 single-centre study of 2,548 men at Michigan Medicine, with scans read by 13 radiologists, looked at what happened after mpMRI using PI-RADS v2. Of the men whose scans were positive, 52.0% turned out to have no clinically significant cancer on subsequent biopsy. That means more than half of the men had a false positive assessment. And, of the men who went on to have a biopsy despite a negative scan, 15.8% did have cancer. That means 15.8% had a false negative assessment and would have had cancer untreated if they had not had the biopsy.
This all points at the same thing. Contemporary prostate MRI is good at locating tissue worth a second look, but not yet good enough to be of diagnostic use. Today, we still run the risk of men being sent for biopsies they do not need, and others being reassured when they should not be.
PSMA-PET has been the other major advancement in imaging technology for prostate cancer. In the randomised proPSMA trial, published in The Lancet, PSMA-PET/CT identified pelvic nodal or distant metastases in high-risk men with 92% accuracy, against 65% for conventional CT and bone scanning. Findings like these solidify a role for PSMA-PET in the staging and recurrence of prostate cancer, i.e finding disease that has spread in men already known to have significant cancer. This use of PSMA-PET to identify distant metastases still leaves the original diagnostic gap of needing a tool to characterise a primary lesion in the prostate gland at first diagnosis. PSMA-PET’s use of radiotracers, as well as the cost and radiation exposure, are likely to limit mainstream diagnostic use.
What Molecular MRI Proposes
Molecular MRI takes a different approach by adding molecular or biological context to the image. Unlike general purpose contrast agents that simply brighten the image, a molecularly targeted agent is engineered to bind a specific biomarker expressed on cancer cells. The presence of a molecular imaging agent in the MRI scan then acts like a beacon, reflecting the molecular signature of the cancer biomarker. In principle, this pairs the spatial resolution of MRI with the kind of molecular specificity usually associated with PET and other nuclear medicine techniques, and does it without ionising radiation, on scanners hospitals already own.
MagSense® Imaging Agent Technology
Imagion Biosystems is building exactly this kind of platform. MagSense® imaging agents’ pair bio-safe iron oxide nanoparticles with targeting molecules, designed for use with standard clinical MRI scanners. The iron is cleared through the liver and metabolised into ferritin, the body’s own iron-storage protein, with no radioactive tracer involved. The lead programme targets HER2+ breast cancer, where a completed Phase 1 study reported no significant safety findings and independent radiologist review confirmed image contrast distinguishable from surrounding tissue. That programme is now in the early stages of a Phase 1b/2 clinical study in the United States.
For prostate cancer, Imagion has developed a PSMA-targeted version of the MagSense® technology leveraging the fact that PSMA is already well established through PET, making it a well-characterised starting point for Imagion’s MRI-based prostate cancer programme. It is early, and there is a long road between a preclinical agent and a clinical one. But the underlying proposition is straightforward: if a contrast agent could report on tumour biology at the moment of first imaging, it could help reduce unnecessary biopsies, support more precise treatment planning and offer a non-invasive way to follow men on active surveillance.
Changing Suspicion Into Certainty
For decades, prostate imaging has been getting better and better at answering “is there something here?” The question that actually decides what happens to a patient is “does this need to be treated?” Molecular MRI is one of the more promising routes to answering it.
Discover what’s beyond the horizon of conventional imaging. Imagion Biosystems is a clinical-stage imaging company pioneering a new category of MRI technology that changes suspicion into certainty. Follow our progress at imagionbiosystems.com, or connect with us on LinkedIn and X. If you are an investigator or potential strategic partner working in this space, we would welcome a conversation about how we might work together.
