MRI Adds Benefits to PSA Screening
Not every man with prostate cancer dies from it; some prostate cancers are very slow growing, and some are very biologically aggressive.
By Stephen Taylor, MD
A PSA screening test is used to help detect prostate cancer. PSA is a substance made by the prostate gland and is elevated in approximately 80% of men with prostate cancer, but an elevation in PSA does not diagnosis prostate cancer. There are other conditions that can cause the PSA to be elevated, such as prostatitis, urinary tract infections, benign enlargement of the prostate with age, trauma to the prostate, etc. Therefore, the PSA test is not perfect.
The PSA value should be compared with the Digital Rectal Exam (DRE), which could reveal a prostate nodule suspicious for cancer or a very large prostate. Until recently, the only way to determine if cancer was present was to perform a Transrectal Ultrasound guided prostate biopsy. Prostate biopsies only take about 10 minutes, and do not cause much pain if a local anesthetic is used. However, prostate biopsies carry certain risks such as infection, hospitalization, and bleeding from the biopsy sites. In addition, prostate biopsies are not perfect either, in that they may miss an “aggressive” cancer (present in between the biopsy sites).
MRI to the rescue!
Just within the past year, a new modality has become available to help determine if men with an elevated PSA or an abnormal DRE actually need a biopsy. This new modality is Multiparametric MRI. A Multiparametric MRI is a 40 minute exam of the prostate. It usually involves injection of a contrast agent, but does not involve x-ray exposure. The radiologist then looks at the images. If an abnormality is identified, the radiologist assigns the area a PIRADS score from 1 to 5. PIRADS stands for Prostate Imaging Recording and Data System. Low PIRADS score lesions (1 -2) have a very low probability of representing aggressive prostate cancer. 60% of men with elevated PSA who undergo a Multiparametric MRI actually have a low PIRADS score, and can be spared from an “unnecessary” biopsy. If the radiologist identifies a high PIRADS score lesion (4-5), there is a 70% chance of having a positive biopsy, and usually these are the aggressive types of prostate cancer that may be life-threatening. These patients are likely to benefit from early treatment. A PIRADS 3 lesion is intermediate, with a 10-20% chance of having a positive biopsy.
Multiparametric MRI also tells us where the cancer lies within the prostate. Software has been developed which allows the MRI image to be transferred to the urologist’s ultrasound screen where the MRI and ultrasound images are fuse together. It is called an MRI-Ultrasound Fusion Guided Biopsy. This allows the urologist to perform accurate targeted biopsies of the suspicious lesion, rather than “blind” systematic biopsies leading to fewer biopsies being performed, and a higher percentage of aggressive cancer is being detected.
MRI is a valuable tool for men who've had previous negative biopsies (sometimes multiple negative biopsies). It is also valuable in men with a rising PSA for which there is no other explanation. Rather than jump to a prostate biopsy, an MRI can help to determine if a biopsy is likely to reveal an aggressive prostate cancer for which early treatment may be lifesaving. I believe the addition of MRI is likely to become the standard approach.
Dr. Stephen Taylor is a Urologist with Pacific Urology. He specializes in robotic urologic surgeries and prostate, kidney and bladder cancers. For more information please call 925-937-7740 or visit www.PacificUrology.com