Micro-ultrasound: The prostate image of the future? Lookin' good, but the jury is still out.

By Howard Wolinsky

Urology office-based micro-ultrasound (micro-US) has been gaining traction as a possible supplement to or replacement for more expensive, hospital-based multiparametric Magnetic Resonance Imaging.

(Outpatient centers can be much cheaper, and involve the same radiologists who do the work in the hospital.)

The race is on. Medicare and commercial insurance cover micro-US as just another type of ultrasound. That’s the good news.

The bad? It can be hard to find doctors who offer the ExactVu device.

Randy AuCoin, CEO of Exact Imaging, the Toronto-based manufacturer, told me about 140 devices are deployed worldwide, 65 in the U.S.

I live in the Chicago area, where medical technology abounds. But the closest micro-US tests are available hours away in St. Louis or Cleveland.

Check here to find your closest ExactVu: https://www.exactimaging.com/physician-finder?

This is, in part, an exercise in medical economics.

Hospitals may not have a strong interest in offering a less-expensive technology that can be performed in a urologist’s office. Their MRI machines need to be kept busy to cover overhead.

Prostate MRI costs anywhere from $500 to $2,500 in the United States, depending upon if they’re performed in a hospital or outpatient center and other factors. (Check this article out on shopping for MRIs: https://www.cnbc.com/2018/08/01/few-patients-use-this-trick-that-saves-on-medical-bills.html)

The cost for a micro-US is supposed to be comparable to that of a transrectal ultrasound. In the Chicago area alone, the range of costs for a transrectal ultrasound goes from $157 to $600, according to HealthCost.com.

But doctors are still awaiting proof of benefits from micro-US, though the news on that is looking good.

Can patients just undergo prostate exams in the urology office and potentially avoid MRIs and biopsies?

The jury is still out.

I have been considering a micro-US since I first heard of it in 2017 at the Prostate Cancer Research Institute in LA.

If my urologist ordered another biopsy—by that point, I had had six since 2010—I was prepared to travel to have a micro-US. But my urologist considers my situation stable and has not suggested another biopsy. I have my bags packed for Cleveland if he does.

Meanwhile, I have moderated two programs on micro-US:

—For AnCan, with Andreas Correa, MD, of Fox Chase in Philadelphia, on micro-US and transperineal biopsies in April 2021:

—For ASPI in May 2021 with Gerald Andreoli, MD, then of WashU in St. Louis and now of Johns Hopkins:

—For ANCAn,

Leonard Gomella, MD, Chairman of the Department of Urology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, writes about micro-US in Practice Update.

“We are in the earliest phase of enthusiasm for this micro-ultrasound technology that may allow urologists to have the advantages of mpMRI lesion identification in the office setting without the need for the preliminary prostate MRI examination. There have already been several changes in the design of the micro-ultrasound probe, circuitry, and refinements in the specific identification tool, PRI-MUS, analogous to the MRI PI-RAD identification protocol. If the benefits of micro-ultrasound are confirmed, it appears that additional urology training will be needed in addition to the purchase of new equipment. Standard urology in-office ultrasound units today are usually multifunctional, and we will need to learn more about how this new platform will function outside of the prostate ultrasound space.”

Lots of news is out on micro-ultrasound, a technique that is competing with multi-parametric Magnetic Resonance Imaging in diagnosing prostate cancer:

--University of Toronto researchers report in the journal Radiology that micro-US is proving comparable to multiparametric Magnetic Resonance Imaging (MRI) in detecting prostate cancer.

However, microultrasound was less successful than mpMRI in preventing biopsies, a major goal for men on active surveillance who don’t want their prostates to be pincushions.

BTW, fun fact: micro-US got its start as a research tool in prostates in lab rats. Its resolution is so good that it can image track marks from previous needle biopsies.

Researchers concluded: “MRI and micro-US showed similar rates of prostate cancer detection, but more biopsies were avoided with the MRI pathway than with micro-US, with no benefit of adding nontargeted systematic biopsy to the MRI- plus micro-US–targeted biopsy pathway. Most MRI lesions were prospectively visible at micro-US, allowing real-time targeted biopsy.” (https://pubs.rsna.org/doi/10.1148/radiol.212163)

The study was prospective, single-center trial enrolling 94 biopsy-naive men with suspected prostate cancer (PCa) between May 2019 and September 2020. All patients underwent multiparametric MRI followed by micro-US, The findings were interpreted blindly, followed by targeted biopsy and nontargeted systematic biopsy using micro-US. 

Urology Today reported: “Micro-ultrasound had a 35% detection rate for clinically significant prostate cancer (csPCa) in comparison to a 39% detection rate for mpMRI. The study authors also noted similar detection rates for clinically insignificant PCa (16% for micro-ultrasound vs. 15% for mpMRI) and cribriform and/or intraductal PCa (14% for micro-ultrasound vs. 15% for mpMRI).”

Researchers pointed out that micro-ultrasound has a fourfold higher crystal density along the transducer, which facilitates a threefold greater increase in spatial resolution.

--Researchers from the University of Toronto and Cleveland Clinic reported in Urology on a study of 25 patients: “MicroUS showed high sensitivity (87%) in detecting index lesions in the prostate gland and identified 100% of index lesions in the peripheral zone.”  (https://www.goldjournal.net/article/S0090-4295(22)00592-1/fulltext)

The researchers said: “All identified lesions were categorized PRI-MUS (the micro-US system similar to MRI’s PI-RADS) score 4 or 5. The three missed index lesions were in the transition zone [median length 10.5 mm (range 4.5-22.5)]. MicroUS missed 11 non index csPCa in nine participants [median length 1.5 mm (range 1.5-10.5)]. Of these, eight were GG2, two GG3 and one GG5. MicroUS identified the csPCa index lesion in all nine of these men.”

—Polish researchers have published a review of ultrasound technologies for the prostate,

Adam Gurwin, MD, of University Center of Excellence in Urology, Department of Minimally Invasive and Robotic Urology, Wroclaw Medical University, and colleagues published their review in the journal Cancers.

They said: “Due to overdiagnosis and overtreatment of a clinically insignificant disease, multiparametric magnetic resonance imaging is recommended for every patient before performing prostate biopsy. However, the diagnostic pathway currently has many limitations and is still far from ideal. Therefore, further alternatives need to be investigated. As the novel ultrasound-based techniques, such as shear wave elastography, contrast-enhanced ultrasound or high-frequency micro-ultrasound are able to, overcome the limitations of magnetic resonance imaging, presenting good performance in recent studies, we have summarized and compared the results of each technique in the detection of PCa”

They note that mpMRI “enabled targeted sampling of the suspicious prostate regions, improving the accuracy of the traditional systematic biopsy. However, mpMRI is associated with high costs, relatively low availability, long and separate procedure, or exposure to the contrast agent. The novel ultrasound modalities, such as shear wave elastography (SWE), contrast-enhanced ultrasound (CEUS), or high-frequency

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micro-ultrasound (MicroUS), may be capable of maintaining the performance of mpMRI without its limitations.

“Moreover, the real-time lesion visualization during biopsy would significantly simplify the diagnostic process. Another value of these new techniques is the ability to enhance the performance of mpMRI by creating the image fusion of multiple modalities. Such models might be further analyzed by artificial intelligence to mark the regions of interest for investigators and help to decide about the biopsy indications. The dynamic development and promising results of new ultrasound-based techniques should encourage researchers to thoroughly study their utilization in prostate imaging.

Gomella notes that “the next big news in this urologic-based micro-ultrasound technology will likely be the results of a planned randomized clinical trial. The OPTIMUM trial will investigate whether micro-ultrasound alone, or in combination with mpMRI, will provide effective guidance during prostate biopsy for the detection of clinically significant prostate cancer. Until the results of that trial are known, it is unlikely that there will be a large shift away from the use of existing TRUS (transrectal ultrasound)  technology, with or without mpMRI fusion, for the diagnosis of prostate cancer.”

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AnCan’s Virtual Support Group for Patients on Active Surveillance is holding a program, “Prostate Cancer Biopsies...The Great Debate,” on whether transrectal biopsies or transperineal biopsies are better for patients.

The program will be 8-9:30 p.m. Eastern on August 29. Register here:  https://bit.ly/3OJ9Mmu

Deborah Kaye, MD, Assistant Professor Duke UniversityDivision of Urology and Duke Clinical Research Institute Margolis Policy Center, will argue for transrectal biopsies. Arvin George, MD, a urologic surgeon specializing in the diagnosis and management of genitourinary cancers at the University of Michigan Health, will argue for transperineal procedures.

Co-sponsors include ASPI, Prostate Cancer Support Canada, the Prostate Forum of Orange County, and TheActiveSurveillor.com.

Please submit questions in advance to moderator Joe Gallo at joeg@ancan.org

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August 27, 2022

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Men, loved ones, and families can gain valuable facts from a cancer genetic test. While the use of genetics testing for cancers is still growing, the existing state of the art for prostate and related cancers is a powerful tool for identifying men and persons at risk. This 60-minute expert presentation will feature expert Geneticist Robert Finch, MS, a Certified Genetic Counselor and Medical Oncologist Michael Glode, MD. You will be reacquainted with prostate cancer screening biomarkers such as the PSA test and a variety of genomic tests, receive a thorough explanation of how and when to get a cancer genetics test along with genomics tests, and finally, a moment for you the patient or family to ask questions. 

As ASPI does not provide medical advice, this program will educate you and your family about medical details of a family history from a genetics test, which genetics tests are not useful for medical care, the pertinent genetic relationships between breast, ovarian, pancreatic, and prostate cancers and how any of these genes may affect your health. and Getting more educated not only better serves the prostate cancer patient, but also the family.