If your doctor suspects you have prostate cancer, undergoing a magnetic resonance imaging (MRI) scan immediately after an initial screening might spare you the medical risks of a prostate biopsy and improve your chances of an accurate diagnosis.
The results of a new British study suggest that MRI scans identified aggressive prostate cancers in men with the disease nearly twice as often as a transrectal ultrasound (TRUS)-directed prostate biopsy. However, among men without aggressive prostate cancers, the MRI incorrectly classified the disease more than twice as often as a TRUS-directed prostate biopsy. The study’s authors contend that if an MRI was used before biopsy to diagnose prostate cancer:
• Nearly one in five deadly cancers missed with current testing methods would be detected
• Unnecessary prostate biopsies would be reduced by 27 percent, and
• Diagnosis of non-aggressive cancers also would be reduced.
The authors, whose findings were published online in January 2017 in The Lancet, note that an MRI scan provides a detailed, computerized image of the prostate and surrounding tissue. By contrast, 12 cores of prostate tissue are taken at random during a TRUS-directed biopsy, so tissue that contains an aggressive cancer elsewhere in the prostate can be missed. They add that biopsies are uncomfortable and can cause bleeding and serious infections, so avoiding some of those procedures would prevent those risks.
In the United States, limited access to qualified personnel to interpret prostate MRIs and the added expense of the scan has discouraged many doctors from ordering the test and third-party payers from covering the cost. And an MRI still may not be effective enough to be used routinely to detect—and rule out—malignant prostate cancers.
What the study found
In The Lancet study, 576 men suspected of having prostate cancer, based on initial screenings or family history, had a standard MRI followed by two types of prostate biopsy—a TRUS-directed biopsy and a prostate-mapping biopsy. The test was performed at hospitals and radiology labs throughout the United Kingdom.
The study's authors note that an MRI scan "tends to detect higher-risk disease and systematically overlooks low-risk disease." For men who had prostate cancer that most physicians would recommend treating, the MRI missed 12 percent of the cases while the TRUS-directed biopsy missed 52 percent. But for nonaggressive cancers, the MRI missed 55 percent while the TRUS-directed prostate biopsy misclassified them just 1 percent of the time.
“Detecting prostate cancers that need to be treated is a real clinical issue for those of us in the trenches treating prostate disease,” says Joel Piser, M.D., a urologist in Berkeley, Calif. “The primary concern in evaluating prostate or bladder symptoms is to rule out a significant malignancy. PSA (prostate-specific antigen) testing has helped but is far from perfect."
Piser says he uses the MRI to stage all newly diagnosed prostate cancer patients to gain valuable information on the extent of the disease and to help predict which patients will benefit from treatment versus active surveillance.
He says the MRI is a great clinical test to help reduce the chance of missing significant cancers in men who have excessive risk factors for biopsies, such as those with prosthetic heart valves, men taking anticoagulation medication, and for those who have an extreme fear of biopsies.
However, not all doctors who treat prostate cancer are convinced that MRI testing will become a part of regular prostate screening just yet. “For that to happen, MRI testing would have to show improved performance in identifying high-grade cancer and would have to be able to exclude high-grade cancer in men without the disease," says H. Ballentine Carter, M.D., professor of urology and oncology at Johns Hopkins School of Medicine in Baltimore. "Further evaluation is needed. In addition, the performance and interpretation of MRIs would need to be standardized.”
If initial screening results from a blood test or digital rectal exam suggest you might have prostate cancer, make an appointment with a urologist for a follow-up evaluation. Make sure it includes a digital rectal exam and a repeat prostate-specific antigen (PSA) test and/or other special blood tests, such as the PHI (prostate health index) or the 4Kscore Test, to determine whether you need a prostate biopsy, Carter says. If the results suggest that a clinically significant prostate cancer may be present, you may want to consider getting an MRI scan to help inform and guide a prostate biopsy.