By: Dan Sperling, MD

For over a decade, evidence has existed that sextant (six core) transrectal ultrasound-guided biopsies were problematic because they either missed cancer, or they failed to capture cells with the highest level of aggression. In the face of diagnostic uncertainty, patients with a negative biopsy but elevated PSA generally wait for a year or more before having a repeat biopsy; or patients found to have cancer have undergone radical treatments regardless of the Gleason grade. A 2001 study by Noguchi, Stamey, McNeal and Yemoto of 222 men whose needle biopsy results were compared with their actual prostatectomy specimens, found a “weak and disappointing correlation.”[i] The biopsy underestimated tumor aggression in 46% of the cases, and overestimated it in 18%. The authors were also concerned that 10% of the patients had insignificant cancer (cancer volume less than 0.5cm) yet still underwent radical prostatectomy when Active Surveillance might have been a safe management strategy until treatment was demonstrated to be necessary. This suggests that TRUS biopsy has been an inadequate tool for planning treatment.

That was nearly 15 years ago, and the use of pre-biopsy MRI is gaining ground. In fact, MRI has the capacity to facilitate accurate detection of tumors, and accurate diagnosis by biopsy—even in patients who have previously had negative TRUS biopsies. Two published studies, both appearing in 2012, address this situation.

The first study, out of Germany (lead author Matthias Roethke) involved 100 patients who had each had one or more previous negative biopsies despite elevated or persistently rising PSA.[ii] Upon imaging with 1.5T MRI, each of them had at least one suspicious area. They subsequently underwent MRI-guided biopsies, and their clinical data noted. 52% of the patients were found to have biopsy-proven prostate cancer. Of those patients, 80.8% had clinically significant cancer, and chose some form of treatment or active surveillance. Thus, they were spared possible future negative biopsies; and they were able to choose a treatment (surgery, radiation or active surveillance) that matched their disease aggression.

The second study, by a Dutch team of researchers (lead author Caroline Hoeks), also involved performing MRI-guided biopsies on men who had at least one previous negative TRUS biopsy.[iii] Their purpose was to determine the detection rate of cancer in men who had cancer-suspicious regions on 3T multiparametric MRI. 265 patients met all inclusion criteria, and were biopsied. 41% were found to have prostate cancer, and of those, 87% were significant—a number in line with the German study.

The fact that MRI and MRI-guided biopsy continue to show high prostate cancer detection rates in comparison with TRUS biopsies opens the door to constructive and, in fact, cost-saving clinical practice. Urologists as a rule do not refer patients for 3T mpMRI (where it’s available). The inefficiencies of repeat TRUS biopsies, and the risks of side effects proportionate to the number of needles taken, should be sufficient to encourage teamwork between urology and radiology in the service of patients. The addition of 3T magnets in both hospital and community settings is a worthwhile investment—and of course this MRI equipment is valuable for countless other applications besides prostate scans.

It is in the physician’s best clinical interest to have the most accurate information about a patient’s disease to develop a management strategy; it is in the patient’s best interest to be equipped with correct knowledge to make a treatment decision. Though change in medicine often occurs slowly, the use of 3T mpMRI to detect prostate cancer can’t come soon enough.