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MRI Improves Prostate Cancer Biopsy Accuracy, Study Finds
New technology spots more aggressive cancer, but fewer low-risk cases
By Dennis Thompson
TUESDAY, Jan. 27, 2015 (HealthDay News) -- Prostate biopsies that combine MRI technology with ultrasound appear to give men better information regarding the seriousness of their cancer, a new study suggests.
The new technology -- which uses MRI scans to help doctors biopsy very specific portions of the prostate -- diagnosed 30 percent more high-risk cancers than standard prostate biopsies in men suspected of prostate cancer, researchers reported.
These MRI-targeted biopsies also were better at weeding out low-risk prostate cancers that would not lead to a man's death, diagnosing 17 percent fewer low-grade tumors than standard biopsy, said senior author Dr. Peter Pinto. He is head of the prostate cancer section at the U.S. National Cancer Institute's Center for Cancer Research in Bethesda, Md.
These results indicate that MRI-targeted biopsy is "a better way of biopsy that finds the aggressive tumors that need to be treated but also not finding those small microscopic low-grade tumors that are not clinically important but lead to overtreatment," Pinto said.
Findings from the study are published in the Jan. 27 Journal of the American Medical Association.
Doctors performing a standard biopsy use ultrasound to guide needles into a man's prostate gland, generally taking 12 core samples from predetermined sections.
The problem is, this type of biopsy can be inaccurate, said study lead author Dr. Mohummad Minhaj Siddiqui, an assistant professor of surgery at the University of Maryland School of Medicine and director of urologic robotic surgery at the University of Maryland Marlene and Stewart Greenebaum Cancer Center in Baltimore.
"Occasionally you may miss the cancer or you may glance the cancer, just get an edge of it, and then you don't know the full extent of the problem," Siddiqui said.
In a targeted biopsy, MRIs of the suspected cancer are fused with real-time ultrasound images, creating a map of the prostate that enables doctors to pinpoint and test suspicious areas.
Prostate cancer testing has become somewhat controversial in recent years, with medical experts debating whether too many men are being diagnosed and treated for tumors that would not have led to their deaths. Removal of the prostate gland can cause miserable side effects, including impotence and incontinence, according to the U.S. National Cancer Institute. But, even if a tumor isn't life-threatening, it can be psychologically difficult not to treat the tumor.
To test the effectiveness of MRI-targeted biopsy, researchers examined just over 1,000 men who were suspected of prostate cancer because of an abnormal blood screening or rectal exam.
The researchers performed both an MRI-targeted and a standard biopsy on all of the men, and then compared results.
Both targeted and standard biopsy diagnosed a similar number of cancer cases, and 69 percent of the time both types of biopsy came to exact agreement regarding a patient's risk of death due to prostate cancer.
However, the two approaches differed in that targeted biopsy found 30 percent more high-risk cancers, and 17 percent fewer low-risk cancers.
"You're missing low-risk cancer. This is the type of cancer where this person certainly would have lived their whole life and died of something else," Siddiqui said.
An MRI is great for guiding doctors to serious cancers, but is not able to detect lesions smaller than 5 millimeters, said Dr. Art Rastinehad, director of focal therapy and interventional urological oncology and an associate professor of urology and radiology at Icahn School of Medicine at Mount Sinai in New York City.
"MRI's greatest weakness is also its greatest strength when it comes to prostate cancer," ignoring low-risk tumors while accurately directing a biopsy to potentially lethal cancers, Rastinehad said. "This study does lay the foundation for a possible paradigm shift in the way we screen men for prostate cancer," he added.
Clinical trials still are needed to show whether MRI-targeted biopsy will save lives or reduce future recurrence of cancer, JAMA Associate Editor Dr. Ethan Basch argued in an editorial accompanying the study. Basch is also director of cancer outcomes research at the University of North Carolina at Chapel Hill.
"A new test should not be widely adopted in the absence of direct evidence showing benefits on quality of life, life expectancy, or ideally both," wrote Basch.
Another open question also remains -- whether the new technology, which requires an MRI for each suspected case of prostate cancer and new equipment to fuse the MRI with an ultrasound scan, would be worth the extra expense.
Pinto believes the new technology might actually save money in the long run, by reducing overtreatment.
"We have to be very thoughtful, especially where health care dollars are scarce, to bring in technology that will not only help men but will be cost-efficient," he said. "That work has not been done completely, although some studies imply this technology may decrease considerably the number of unnecessary biopsies performed every year, and so could help control costs."
For more on prostate cancer, visit the U.S. National Cancer Institute.
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