MRI for prostate biopsies increases odds of finding aggressive tumors

Prostate biopsies performed using magnetic resonance imaging (MRI) are more likely to find aggressive tumors than those that rely on ultrasound, suggests a new study at Washington University School of Medicine in St. Louis.

The research is presented May 19 at the meeting of the American Urological Association in Orlando, Fla.

Prostate biopsies often are recommended when blood levels of prostate-specific antigen (PSA) rise above 4.0 ng/ml. Typically, the procedures are performed using ultrasound to guide the placement of biopsy needles into the prostate. But ultrasound is not sensitive enough to visualize suspicious areas that might indicate cancer. So, urologists randomly distribute needles into the prostate to withdraw tissue samples for analysis.

“Biopsies performed under ultrasound guidance are very much hit or miss,” said prostate cancer expert Gerald Andriole, MD, chief of urology at Washington University School of Medicine and Barnes-Jewish Hospital. “If a biopsy is negative, there’s a significant chance that it missed a cancer, and if it’s positive, there’s a tendency to treat the cancer aggressively due to concerns that the biopsy missed an aggressive component of the cancer. This leads to many men receiving excessive treatment.”

Each year in the United States, about 1 million men undergo prostate biopsies, but only about 20 to 25 percent are positive. The procedure can be painful and comes with a risk of bleeding and infection.

In recent years, Andriole and other leading urologists have been investigating whether targeted biopsies performed using MRI to visualize suspicious areas of the prostate are more likely to be accurate. Washington University is the only center in the St. Louis region where targeted prostate biopsies are performed using MRI guidance.

In the new study, Andriole and radiologists at the Mallinckdrodt Institute of Radiology evaluated their experience with MRI-guided prostate biopsies in 70 men who had the procedure at some point from December 2010 to July 2013. The men’s average age was 65, and their PSA scores averaged just above 8.0 ng/ml.

The biopsies were performed after results of MRI scans of the prostate were available. For each biopsy, he took multiple tissue samples in areas of the prostate that looked suspicious for cancer as well as in nonsuspicious areas where cancers may have been too small to visualize with MRI.

The analysis showed that biopsies targeted to suspicious areas of the prostate were nearly three times more likely to find cancer than those targeted to nonsuspicious areas. Further, biopsies targeted to suspicious areas were four times more likely to detect aggressive tumors that warranted treatment. Such tumors have a Gleason score of 7 or more.

The Gleason scoring system measures tumor aggressiveness based on biopsy results and can range from 1-10, with 10 being the most aggressive.

MRI is not perfect, Andriole noted. In this study, it accurately predicted a positive biopsy 62 percent of the time.

For men with elevated PSAs, biopsies targeted to suspicious areas with MRIs missed about 7 percent of aggressive tumors. By comparison, ultrasound biopsies typically miss up to 20 percent of aggressive cancers.

But as MRI technology improves, Andriole thinks prostate cancer screening eventually could be like mammography screening for breast cancer. If a mammogram is negative, there’s no need for a biopsy, but if it’s positive, a targeted biopsy is performed to confirm or rule out cancer.

“We hope to get there with prostate cancer,” said Andriole, the Robert Killian Royce, MD, Distinguished Professor of Urologic Surgery. “In the future, if a man has an elevated PSA, we’d like to do an MRI and be so confident in the technology that we’d only do a targeted biopsy if the MRI were positive. We’re not there yet, but that’s the goal.”

Funds from the Midwest Stone Institute and the St. Louis Men’s Group Against Cancer supported this research.

Washington University School of Medicine’s 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children’s hospitals. The School of Medicine is one of the leading medical research, teaching and patient-care institutions in the nation, currently ranked sixth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children’s hospitals, the School of Medicine is linked to BJC HealthCare.