Magnetic resonance imaging (MRI) and MRI-guided prostate biopsy can greatly reduce the detection of low-risk prostate tumors while increasing detection of intermediate- and high-risk tumors, according to the findings of a recent study.
Leslie C. Thompson, MBBS, FRACS, a consultant urologist at The Wesley Hospital and Wesley Research Institute in Brisbane, Australia, and colleagues compared multiparametric MRI (mpMRI) followed by MRI-guided biopsy (MRGB) with transrectal ultrasound-guided biopsy (TRUSGB) in the detection of prostate cancer (PCa) in 223 biopsy-naïve men referred by urologists with a high or concerning PSA level.
Of these, 142 (63.7%) had PCa. TRUSGB detected 126 cases of PCa in 223 men (56.5%), including 47 (37.3%) classified as low risk and 79 (62.7%) classified as intermediate or high risk. MRGB detected 99 cases of PCa in 142 men (69.7%) with equivocal or suspicious mpMRI findings. Of these, 6 (6.1%) were low risk and 93 (93.9%) were intermediate or high risk. MRGB detected intermediate- or high-risk tumors in 29 men that were either missed or misclassified as low risk by TRUSGB, Dr. Thompson’s team reported online ahead of print in European Urology.
The MRGB pathway decreased the need for biopsy by 51%, decreased the diagnosis of low-risk PCa by 89.4%, and increased detection of intermediate- or high-risk PCa by 17.7%, the researchers reported.
All men in the study underwent mpMRI. Patients returned for prostate biopsy at a second visit. Patients with equivocal or intermediate- or high-risk lesions underwent MRGB followed within 30 minutes by TRUSGB performed by a urologist blinded to the mpMRI findings and MRGB procedure. A 12-core TRUSGB was performed in a standard paired sextant pattern. Patients with normal mpMRI scans had TRUSGB only.
The study’s most important finding, Dr. Thompson told Renal & Urology News, is that the MRI-based diagnostic pathway “almost eliminates the diagnosis of low-risk cancer. This relieves a huge psychological, investigative, and treatment burden on men that have been told they have ‘insignificant’ cancer, because they and their doctors only hear one word: ‘cancer.’”
He continued: “It has become clear to me that the reason that both urological groups and government task forces have not been able to produce sustainable guidelines for PSA testing over the last 20 years is that they have been, unknowingly, addressing the wrong question, over and over again.
The PSA test, in retrospect, is not the problem: It is merely a non-specific ‘alarm bell’ that something is wrong with the prostate. The problem, in retrospect, seems to be the current biopsy protocols where we take large numbers of random biopsies from the prostate.”
With respect to implementing mpMRI and MRGB in prostate cancer workups, Dr. Thompson stated that collaboration between urologists and radiologists is paramount. Urologists are expert in prostate anatomy, surgery, and diseases, whereas radiologists are expert in imaging.
Urologists will have to learn about MRI as well as how to recognize good image quality. They also will have to insist on good image quality from their radiologists, he said.