Magnetic resonance imaging (MRI) may not be the best diagnostic choice universally for all men suspected of having prostate cancer, according to researchers at Weill Cornell Medicine and NewYork-Presbyterian. While recent studies have demonstrated that MRI is more accurate in detecting tumors than other diagnostic procedures, there are barriers that prevent the technique’s widespread use.
In an editorial published Sept. 13 in JAMA Oncology, Dr. Jim Hu, the Ronald P. Lynch Professor of Urologic Oncology at Weill Cornell Medicine and director of the LeFrak Center for Robotic Surgery at NewYork-Presbyterian/Weill Cornell Medical Center, argues that significant limitations — including cost and radiology expertise — stand in the way of fully implementing MRI as the primary diagnostic tool for prostate cancer.
“What we want people to understand is that there are significant challenges to accepting wholesale that MRI should be the new standard of care,” Dr. Hu said, “and the benefit of MRI’s increased diagnostic capabilities needs to be balanced against those costs.”
Prostate cancer screening begins with a blood test that monitors levels of prostate-specific antigen (PSA), a protein produced by all prostate cells. Elevated PSA levels may indicate the presence of prostate cancer; men suspected of having the disease are typically referred for ultrasound-guided biopsy. But prostate biopsy carries risks, including infection and difficulty urinating after the procedure.
PRECISION (Prostate Evaluation for Clinically Important Disease: Sampling Using Image guidance or Not?), a multicenter study with results published in March in the New England Journal of Medicine, sought to determine whether a diagnostic MRI could be used instead of biopsy to rule out prostate cancer. The study looked at 500 men suspected of having the disease after PSA testing. They either received the standard-of-care diagnostic test (ultrasound-guided biopsy) or MRI without biopsy. Men who had abnormal findings on MRI then went on to targeted biopsy.
“We demonstrated a 12 percent absolute improvement of the rate of cancer detection for those who had MRI prior to biopsy and MRI targeted biopsy compared with men who just had ultrasound-guided biopsy,” said Dr. Hu, who was also an investigator on PRECISION. “This is the first Level I evidence that MRI-targeted biopsy is superior.” In addition, 28 percent of men in the study’s MRI group were able to avoid biopsy when their imaging showed no evidence of cancer.
Although the results of PRECISION have been hailed as great news for prostate cancer diagnosis, MRI has drawbacks that currently make using it as the standard of care impractical, Dr. Hu said. The first barrier is cost. Prostate MRI costs anywhere from $500 to $2,500 in the United States, depending upon a patient’s insurance coverage. Approximately 1 million American men are currently sent for prostate biopsy every year. If all of those men received MRI instead, costs could reach $3 billion annually.
The second barrier to MRI implementation is lack of expertise. “There are many community hospitals in the United States that don’t even do prostate MRI,” said Dr. Hu, who has also served on the speakers’ bureau for Genomic Health. And those that do may not have accurate readings. In fact, studies have shown that prostate MRI results from community hospitals only agree with those done at high-volume, expert facilities 54 percent of the time. “The test is only valuable if the results are accurate and right now we can’t guarantee that across the board,” he said.
Working within these limitations is critical to the future of prostate cancer diagnosis, Dr. Hu said. Scaling up prostate MRI capabilities at hospitals throughout the country will take time and significant expense. “In the meantime, we need to look at this in the wider context of what is available to us right now.”
Dr. Hu and colleagues propose using prostate biomarker tests to assess risk in men with elevated PSA. These tests, including free-to-total PSA ratio, Prostate Health Index (a mathematical formula that combines three different PSA variants) and the 4k score (which measures four different prostate-specific enzymes), measure other markers for prostate cancer in the blood. “We can use these tests to better assess up front who needs an MRI and biopsy,” he said. “Unfortunately, routine use of MRI for every patient with elevated PSA is just not practical at this time.”