Biopsies guided by high-resolution ultrasound may be as effective as those using magnetic resonance imaging (MRI) in diagnosing prostate cancer, an international clinical trial has shown. The technology, called micro-ultrasound, is cheaper and easier to use than MRI. It could significantly speed up diagnosis, reduce the need for multiple hospital visits, and free up MRI for other uses, researchers reported. The results of the OPTIMUM trial were presented at the European Association of Urology (EAU) Congress 2025 in Madrid (Abstract GC6) and simultaneously published by Kinnaird et al in JAMA.
OPTIMUM is the first randomized trial to compare microultrasound (microUS)-guided biopsy with MRI-guided biopsy for prostate cancer detection. It included 677 men who underwent biopsy at 19 hospitals across Canada, the United States, and Europe. Of these, half underwent MRI-guided biopsy, a third received microUS-guided biopsy followed by MRI-guided biopsy, and the remainder received microUS-guided biopsy alone.
MicroUS was able to identify prostate cancer as effectively as MRI-guided biopsy, with very similar rates of detection across all three arms of the trial. There was little difference even in the group who received both types of biopsies, with microUS detecting the majority of significant cancers.
Background and Clinical Significance
Most prostate cancer biopsies are conducted using MRI images fused onto conventional ultrasound, as this enables urologists to target potential tumors directly, leading to more effective diagnosis. MRI-guided biopsy requires a two-step process (the MRI scan followed by the ultrasound-guided biopsy), requiring multiple hospital visits and specialist radiological expertise to interpret MRI images and fuse them onto the ultrasound.
MicroUS has higher frequency than conventional ultrasound, resulting in three times greater resolution images that can capture similar detail to MRI scans for targeted biopsies. Clinicians such as urologists and oncologists can be easily trained to use the technique and interpret the images, especially if they have experience in conventional ultrasound. MicroUS is less expensive to acquire and continuously run compared to MRI and could enable imaging and biopsy to be carried out during one appointment—even outside a hospital setting.
The results of the OPTIMUM trial could have a similar impact to the first introduction of MRI, according to the lead trial investigator, Laurence Klotz, MD, Professor of Surgery at the University of Toronto’s Temerty Faculty of Medicine and the Sunnybrook Chair of Prostate Cancer Research.
“When MRI first emerged and you could image prostate cancer accurately for the first time to do targeted biopsies, that was a gamechanger,” he recalled. “But MRI isn’t perfect. It’s expensive. It can be challenging to get access to it quickly. It requires a lot of experience to interpret properly. And it uses gadolinium, which has some toxicity. Not all patients can have MRI[—like] if they have replacement hips or pacemakers, for example.”
“But we now know that microUS can give as good a diagnostic accuracy as MRI and that is also game-changing,” he continued. “It means you can offer a one-stop shop, where patients are scanned [and] then biopsied immediately if required. There’s no toxicity. There are no exclusions. It’s much cheaper and more accessible. And it frees up MRIs for hips and knees and all the other things they’re needed for.”
Jochen Walz, MD, of the Institut Paoli-Calmettes Cancer Center, Marseille/France, is a leading expert in the field of urological imaging and a member of the EAU Scientific Congress Office. Commenting on the findings from OPTIMUM, he said, “This is a well-conducted and exciting study which adds a very important tool to the diagnosis of prostate cancer. Using microUS is a more straightforward and simpler process. This also makes it safer by avoiding the potential errors that can creep in during the transfer of MRI to ultrasound for a fusion biopsy.”
“It does require training to spot the patterns and interpret microUS images correctly. But once that’s been mastered, then it could enable prostate cancer diagnosis and biopsy to happen at the same appointment,” he highlighted. “It could also make targeted biopsies more available in less developed health-care systems where MRI is a very precious resource. The ease and cost of microUS means it could be an important tool for screening programs as well, but further research would be needed to understand its potential role in that setting.”
Disclosure: The trial was sponsored by Canadian company Exact Imaging, which has developed the microUS technology. For full disclosures of the study authors, visit resource-centre.uroweb.org.
