Prostate MRI and Targeted Biopsy
Multiparametric MRI (MP-MRI) provides a three-dimensional image of the prostate, giving important information about the cancer’s location, size, and how “aggressive” it appears. MP-MRI also greatly increases the confidence that higher-grade cancers are not being overlooked in men on active surveillance. MP-MRI is usually performed without an endorectal coil.
“Multiparametric” Means Four Scans in One
There are four different imaging components to MP-MRI. The first is called “T2-weighted,” which creates the clearest images and gives the most capsular detail. The second and third parameters are called diffusion-weighted imaging (DWI) and the apparent-diffusion coefficient (ADC). These provide information about the aggressiveness of the tumor. The fourth, called dynamic-contrast enhancement (DCE), maps the blood flow of the tumor.
“PI-RADS”
PI-RADS (prostate imaging reporting and data systems) compiles a score composed of all four parameters—T2, DWI/ADC, and DCE—on a 1-to-5 scale. Lesions with a score of 4 or 5 are more likely to represent clinically significant prostate cancer (Gleason 4+3=7 or higher). Once MP-MRI detects a suspicious lesion, a targeted biopsy can be performed.
Evaluating Undiagnosed Men with High PSA Levels
There are notable advantages of MP-MRI over the random 12-core biopsy. First, it is less likely to diagnose clinically harmless cancers, sparing patients from unnecessary anxiety. Second, well-performed MP-MRI only misses significant cancer about 10 percent of the time, and these missed cancers tend to be small and unlikely to spread. To put this in perspective, a well-performed 12-core random biopsy misses high-grade cancer 25 percent of the time.
MRI for Active Surveillance
Until recently, men on active surveillance have only been monitored with periodic random 12-core random biopsies and PSA testing. MP-MRI provides three advantages over random biopsy. First, imaging is noninvasive. Second, imaging can find suspicious areas that might have been missed by previous random biopsies. Third, imaging provides a baseline measurement of the cancer’s size that can be used for follow-up monitoring to detect enlargement. As logical as imaging sounds, active surveillance strategies currently performed in most academic centers do not yet routinely use MP-MRI to detect cancer progression. Nevertheless, this concept is gaining traction.
The Future of Prostate MRI
The same imaging techniques for identifying prostate cancer for targeted biopsy can also be used to direct treatment. Focal therapy spares much of the surrounding normal prostate tissue from unnecessary damage. Given the increasing reliance on accurate imaging for state-of-the-art care, the importance of finding centers of excellence with skilled and experienced physicians will assume greater and greater importance.
Daniel Margolis, MD earned his bachelor’s degree from Berkeley and his doctorate from USC, followed by an internship in internal medicine at West Los Angeles Veteran's Administration Hospital. He completed his residency in Diagnostic Radiology at UCLA, and a prestigious fellowship funded by the National Cancer Institute at Stanford. When he was in medical school, his former college roommate’s wife was diagnosed with breast cancer while she was pregnant with their third child. She succumbed to her disease within a few years, which had a pronounced effect on him. He chose to pursue a cancer-based fellowship, after which he stayed in private practice in the Bay Area. During that first year, a high school friend of his was diagnosed with pancreatic cancer, which sadly overtook her, too, again leaving behind a grieving widow and young children. Dr. Margolis decided then that being purely a diagnostic radiologist was not making the most use of his training, and took a job at UCLA where he could apply his skills to cancer research, achieving the most success with prostate imaging. He now serves as the Associate Professor of Radiology and Director of Prostate MRI at Weill Cornell in New York.