Biopsies guided by high-resolution ultrasound have been shown to be as effective as those using MRI in diagnosing prostate cancer; and could significantly speed up diagnosis, reduce number of hospital visits, and free up MRI for other uses.
“This is practice changing for the diagnosis of prostate cancer: we can offer patients a one-stop shop, where they are imaged and then biopsied immediately, if required,” says Dr. Laurence Klotz, principal investigator of the trial and the Sunnybrook Chair of Prostate Cancer Research. “There’s no toxicity, no exclusions, it’s easier to use, and is much cheaper and more accessible; freeing up MRIs for hips and knees and all the other things they’re needed for.”
In a large international clinical trial, the study investigators compared micro-ultrasound (microUS) – a high-frequency ultrasound technology first pioneered by Dr. Stuart Foster’s lab in the 1990s at Sunnybrook Research Institute – with MRI-guided biopsy for prostate cancer. The results of the OPTIMUM trial are being presented on March 23 at the 2025 European Association of Urology Congress (EAU25) in Madrid and published in JAMA.
OPTIMUM is the first randomized trial to compare microUS-guided biopsy with MRI-guided biopsy for prostate cancer, involving 677 men who underwent biopsy at 19 hospitals across Canada, the USA 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.
In the study, 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 the microUS detecting the majority of significant cancers.
Around a million prostate cancer biopsies are carried out each year in Europe, a similar number in the USA and around 100,000 in Canada. The majority of biopsies are conducted using MRI images fused onto conventional ultrasound, as this enables urologists to target potential tumours 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 the 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 (of minute details within tissue) to MRI scans for targeted biopsies. Cheaper to buy and run compared to MRI, micro-US could enable imaging and biopsy to be carried out during one appointment, even outside a hospital setting.
Clinicians such as urologists and radiologists can be easily trained to use the technique and interpret the images, especially if they have experience in conventional ultrasound.
The results of the OPTIMUM trial could have a similar impact to the first introduction of MRI, according to Dr. Klotz, also a professor of surgery with the Temerty Faculty of Medicine at University of Toronto:
“When MRI first emerged, and you could image prostate cancer accurately for the first time to do targeted biopsies, that was a gamechanger,” he recalls. “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. It uses gadolinium which has some toxicity, and not all patients can have MRI, if they have replacement hips or pacemakers, for example.
And it’s a Canadian innovation success story – the technology was developed right here at Sunnybrook.”
The company Exact Imaging sponsored the trial.
Media contacts:
Sunnybrook Health Sciences Centre
Nadia Norcia
nadia.norcia@sunnybrook.ca
416.480.4040
Temerty Faculty of Medicine, University of Toronto
Blake Eligh
blake.eligh@utoronto.ca