Not long ago, an abnormal PSA reading would be followed right away by a standard biopsy to search for potential cancer in the prostate. During such a procedure, doctors take 10 to 12 samples of the prostate from various locations while looking at the gland with an ultrasound machine.
These days, however, men with high PSA levels during cancer screening might be offered a specialized imaging test first. Called a multiparametric magnetic resonance imaging (mpMRI) scan, it’s particularly good at visualizing cancer in the prostate and distinguishing high-grade tumors that need immediate treatment from low-grade tumors that don’t. Furthermore, if the scan is positive for cancer, then it’s also more effective than ultrasound at guiding doctors to suspicious areas of the prostate during a subsequent biopsy, so they can take fewer samples.
But what if the mpMRI is negative? Can a man avoid having a biopsy altogether, along with the risk of infection and other complications that might come with it? Or should he still have a standard biopsy to rule out cancer that the radiologist or the MRI might have missed?
These are important questions that specialists are now grappling with.
European guidelines say yes
In newly updated guidelines, the European Association of Urology came out in favor of omitting a first biopsy for a man with abnormal PSA and a negative mpMRI, but only if his suspected risk for aggressive cancer is low, and he has discussed the pros and cons of forgoing the exam with a doctor. The UK’s national health agency reached a similar conclusion the previous December. Still, divisions in the field remain. Half of the urologists queried on the topic during a presentation at the EAU’s annual meeting in Barcelona last March (which drew 10,000 attendees) voted in favor of the standard biopsy for men with a negative mpMRI.
American guidelines say no
Here in the United States, professional organizations have also expressed their reservations: the American Urological Association, for instance, warns in its current guidelines that the risk of missing clinically significant prostate cancer on a negative mpMRI raises persistent concerns.
During a recorded conversation hosted by Grand Rounds in Urology, Dr. Sigrid Carlsson, a physician-epidemiologist from the Memorial Sloan Kettering Cancer Center in New York, acknowledged that while men would understandably want to avoid a biopsy, radiologists vary significantly in how well or accurately they read mpMRIs, and miss rates (i.e., the numbers of truly existing cancers missed either by the radiologist or by the mpMRI itself) can range up to 20%. The false negative diagnoses occur most frequently among radiologists who are just learning how to interpret the scans, and for that reason, she said, “We can’t avoid biopsy if the mpMRI is negative because the miss rate is so high.”
Dr. Anthony D’Amico, a professor at Harvard Medical School and an author on the AUA guidelines, gave the same reason to back his view that a standard 12-core biopsy should still be undertaken despite negative mpMRI readings.
However, Dr. Veeru Kasivisvanathan, a urologist from University College London, took an opposing view. He argued that if the mpMRI is of good quality and interpreted by an adequately trained radiologist, then the risk of harboring significant cancer is low enough that biopsy can be safely avoided. “Equally, some patients will value more certainty and might wish to go ahead with a biopsy despite having a low risk of cancer and a negative mpMRI — this is still a valid option,” he said.
The decision to biopsy or not could be aided with better diagnostic tools, and one cited repeatedly is PSA density, or the total amount of PSA in blood divided by the prostate volume. High PSA densities denote higher risk, and when combined with mpMRI findings, could enable patients to make a more informed choice.
According to Dr. Marc Garnick, Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor in chief of HarvardProstateKnowledge.org, diagnostic uses for mpMRI are only now emerging, and patients should carefully weigh their options with a doctor before deciding whether or not to proceed to biopsy in the event of a negative scan. Years of further study, he said, will reveal how outcomes vary among those who choose a biopsy versus those who don’t. However, for men who have already had a standard 12-core biopsy and require another in the future, Dr. Garnick added, then MRI guidance is helpful for targeting only abnormal areas and reducing the risk of potential complications.