Micro-ultrasound proves to be better than MRI in diagnosing prostate cancer

Micro-ultrasound proves to be better than MRI in diagnosing prostate cancer

Biopsies guided by high-resolution ultrasound are just as effective as those using 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 say.

The results of the optimal study will be presented today [Sunday March 23, 2025] at the European Association of Urology Congress in Madrid and published inJama.

Optimum is the first randomized trial comparing micro-ultrasound biopsy with MRI-guided biopsy for prostate cancer. It includes 677 men who underwent biopsy at 19 hospitals in Canada, the United States and Europe. Of these, half underwent MRI-guided biopsy, a third underwent microguided biopsy followed by MRI-guided biopsy, and the remainder underwent microguided biopsy alone.

Microus was able to identify prostate cancer as effectively as an MRI-guided biopsy, with detection rates very similar across all three arms of the study. Even in the group that received both types of biopsies, there was little difference, with micro-detection detecting the majority of significant cancers.

Around one million prostate cancer biopsies are performed each year in Europe, a similar number in the United States and around 100,000 in Canada. The majority of biopsies are performed using MRI images fused onto traditional ultrasound fusions, as it allows urologists to directly target potential tumors, resulting in a more effective diagnosis. MRI-guided biopsy requires a two-step process (the MRI scan followed by the ultrasound-guided biopsy) that requires multiple hospital visits and specialized radiology expertise to interpret the MRI images and fuse them onto the ultrasound.

Micro-ultrasound has a higher frequency than traditional ultrasound, resulting in three times larger resolution images that can capture similar details 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 with conventional ultrasound. Microus is cheaper to buy and run compared to MRI and can allow the imaging and biopsy to be performed outside of a hospital during one appointment.

The results of the optimal study could have similar effects as the first introduction of MRI, according to lead researcher in the study, Laurence Klotz, professor of surgery at the Temerty Faculty of Medicine and chair of Sunnybrook Chair of Prostate Cancer Research, professor of surgery at the Temerty Faculty of Medicine at the University of Toronto.

“When MRI first came along and you could first accurately visualize prostate cancer to do targeted biopsies, that was a game changer,” he recalls. "But MRI is not perfect. It is expensive. It can be difficult to get access to quickly. It requires a lot of experience to interpret correctly. And it uses gadolinium, which has some toxicity. Not all patients can have MRI if, for example, they have replacement heartbeats or pacemakers.

"But we now know that Microus can give as good a diagnostic accuracy as MRI and that it's also a game changer. They can offer a one-stop shop where patients are scanned and then immediately biopsied if necessary. There is no toxicity. There are no exclusions.

Professor Jochen Walz from the Institut Paoli-Calmettes Cancer Center in Marseille/France is a leading expert in the field of urological imaging and a member of the Eau Scientific Congress Office.

He said: "This is a well-conducted and exciting study that adds a very important tool to the diagnosis of prostate cancer. Using micro-ultrasound is a simpler and easier process. This also makes it safer by avoiding the potential errors that can occur during the transfer of MRI into fusion biopsy.

"It requires training to recognize the patterns and correctly interpret micro-ultrasound images. Once mastered, it may enable diagnosis of prostate cancer and biopsy at the same appointment. It could also make targeted biopsies available in less developed healthcare systems where MRI is a very valuable resource.

"The ease and cost of micro-ultrasound means it could also be an important tool for screening programs, but further research would be needed to understand its potential role in this setting."

The trial was sponsored by Canadian company Exact Imaging, which developed the micro technology.

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