MRI and Prostate Cancer
Choosing Where to Have Your MRI Is Key to Getting an Accurate Diagnosis
Until recently, a patient with abnormally high prostate-specific antigen (PSA) level would be sent for a biopsy to determine if he had prostate cancer. This biopsy is guided by ultrasound, which urologists use to take twelve samples of the prostate—in an attempt to find cancer regardless of where it is in the gland.
As a diagnostic tool for prostate cancer, however, ultrasound is limited. The ultrasound images show the prostate gland well enough to guide the twelve samples, but ultrasound often does not show the cancer inside the prostate. As a result, a biopsy may miss aggressive prostate cancer and may instead discover indolent prostate cancer that need not be treated.
“Ultrasound may not find the bad cancer, and sometimes it identifies cancers that would be better left alone,” says Dr. Hiram Shaish, assistant professor of radiology at Columbia University Irving Medical Center.
Now, men with high PSA levels are more and more frequently being offered a specialized test called multiparametric magnetic resonance imaging (mpMRI). mpMRI provides high-quality imaging that can visualize cancer in the prostate, distinguishing tumors that need to be treated from insignificant tumors that do not.
"A high-quality, well-interpreted prostate MRI can help avoid a prostate biopsy in some patients,” says Dr. Shaish, referring to the fact that low-grade, non-life threatening tumors are often not visible on mpMRI. And when cancer is detected with this scan, the mpMRI images can be fused onto the ultrasound images during a biopsy, making suspicious lesions more visible for a more accurate detection of potentially life-threatening prostate cancer.
But not all MRI studies are equal, and patients often aren’t aware of the differences when they schedule an exam. “The way it’s done and the way it’s read make a huge difference,” says Dr. Shaish. “It’s very important for patients to have their MRI performed and interpreted properly.”
Given the insurance restrictions around this costly exam, patients basically have one chance to get it right.
The quality of the MRI system is critical to getting the right diagnosis. Equally important is the radiologist who reads the scan. “There are a lot of radiologists who are good radiologists,” says Dr. Shaish, “but that’s not the same as someone who’s been specifically trained in prostate MRI and who has read hundreds of these studies at a facility where high quality exams are performed.”
How can a patient make sure he is getting the scan he needs for a proper diagnosis? A few questions upon scheduling will help determine whether he is getting the quality he needs from both the MRI system and the radiologist who will read the results:
How old is your MRI scanner?
Because technology changes so quickly and prostate MRI is a relatively new type of study, a scanner should ideally be less than ten years old. Larger, academic institutions are more likely to purchase updated scanners and update the software regularly.
What is the strength of the MRI scanner?
The field strength of the MRI magnet is measured in teslas, and systems can range between .5T and 3T. A 3T scanner will provide the radiologist with the highest quality images in the case of the prostate gland which is a very small organ. Images from a scanner with a weaker field strength could potentially lead to an inaccurate diagnosis. “We give a lot of second opinions of scans that have been performed elsewhere,” says Dr. Shaish. “Often the quality isn’t high enough, and we can’t provide the diagnosis that the patient needs.”
Will the MRI be done with an endorectal coil or an external pelvic coil?
Some radiology practices use an endorectal coil – a probe-like device covered with latex – which is inserted into the rectum and helps provide high-quality images of the prostate. With a newer, high-quality MRI system, endorectal coils are not necessary and an external pelvic coil can be used instead, eliminating patient discomfort while maintaining high quality images.
Has the radiologist who will read the study undergone PI-RADS®-specific prostate MRI training?
The Prostate Imaging Reporting and Data System, or PI-RADS®, refers to standards that have been developed by several organizations to improve early diagnosis and treatment of prostate cancer.
Prostate cancer is the most commonly diagnosed cancer in men, with one out of nine men diagnosed in their lifetime. And while many cases don’t require treatment, it is a leading cause of cancer death among men, second only to lung cancer. The broad range between cancer that does not require treatment and life-threatening prostate cancer means that proper diagnosis is key to determining next steps.