OPTIMUM is the first randomized trial to compare microultrasound (microUS)-guided biopsy with MRI-guided biopsy for prostate cancer. It involves 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 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 United States, 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 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 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 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 cheaper to buy and run compared with 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 lead researcher on the trial, Laurence Klotz, a 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 game-changer,” 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. And it uses gadolinium which has some toxicity. Not all patients can have MRI, 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. It means you can offer a one-stop shop, where patients are scanned, 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.”
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 European Association of Urology Scientific Congress Office. He says, “This is a well-conducted and exciting study which adds a very important tool to the diagnosis of prostate cancer. Using microultrasound 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 microultrasound images correctly. But once that’s been mastered, then it could enable prostate cancer diagnosis and biopsy to happen at the same appointment. 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 microultrasound mean 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.”
The trial was sponsored by Canadian company Exact Imaging, which has developed the microUS technology.
— European Association of Urology