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    Prostate MRI has value, but results are not ‘gospel’

     

    Give us your thoughts about using MRI in three scenarios: for upfront screening, an active surveillance situation, and in patients with a previous negative biopsy with PSA still rising. Starting with primary screening, what are some of the challenges and benefits of its use in each of those areas?

    Primary screening would involve a man with an elevated PSA, suggesting clinical risk of prostate cancer. Obtaining an MRI before the first biopsy to minimize the number of men who need a biopsy or target areas that might have higher risk cancers makes a lot of sense. But as of right now, the cart is before the horse.

    The good news is there are trials in this space. One published study, PROMIS (PROstate MRI Imaging Study), suggests this strategy might be useful. Importantly, that trial was done in Europe where MRIs are significantly less expensive. In the U.S., a few sites are now participating in an international trial that recently completed accrual, and our center is fortunate enough to be one of them. It’s called the PRECISION trial (PRostate Evaluation for Clinically Important Disease: Sampling Using Image-guidance Or Not?), which is addressing the same question.

    Read: How do height, adiposity affect prostate Ca risk?

    Importantly, I do not think it’s good-quality care right now for every man going for his first biopsy to have an MRI beforehand. The National Comprehensive Cancer Network (NCCN) guidelines specifically say it is not the standard of care but there’s emerging evidence that it might be useful at some point.

     

    The obvious concerns with prostate biopsy are the infectious complications and resistant organisms, which appear to be increasing, and MRI alone could possibly eliminate that problem. If MRI was used as a screening tool and you still didn’t find cancer, would you still not do a random biopsy?

    That’s where it’s very important to look at your own institution’s data, which I realize sounds “ivory tower-ish.” However, I can share an example from our institution. Historically, based on the published data, men at our center with a “negative MRI” always had a systematic biopsy out of fear of missing meaningful cancers that weren’t visualized on MRI. We then looked at our own data, which shows that if you have a negative MRI, there’s only a 5% chance a biopsy-detectable Gleason 7 cancer or higher was present. I share that information with men. Most men will say, if the risk is only 5%, they’re going to skip the biopsy. Other men still want to proceed.

    The totality of the data in the urologic literature varies with respect to that percentage, but it ranges from as low as 1.83% risk of Gleason 7 or higher with a negative MRI in an Italian study to as high as about 16% in some earlier MRI studies.

     

    Another big issue, as you well know, relates to the quality of the MR images and the expertise of the people reading them.

    At our center, a lot of patients come in with outside MRIs, and we load them into our system. I uniformly show the images to our best prostate radiologist and ask him: Is this a quality MRI? If the answer is no, we repeat it. If the answer is yes, I have him read that MRI, and his reading sometimes agrees with the outside radiologist and often does not. We really rely on his expertise.

    Next: MRI and active surveillance

    J. Brantley Thrasher, MD
    Dr. Thrasher, a Urology Times editorial consultant, is professor and chair of urology at the University of Kansas Medical Center, Kansas ...

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    • UBM User
      I am a medical oncologist specializing in prostate cancer (PC) since 1983, and have had an extended experience with prostate MRI for over 2 decades. The discussion above by Eggener and Thrasher is very reasonable but a few points are worth mentioning. 1. I would not want any patient under my guidance studied with a 1.5T MRI. At the very least 3T should be routine. In the near future we will likely see 7T being used given the more discrete anatomy revealed. 2. There should be OBJECTIFIED data and less emphasis on "narrative", the latter of which tends to encourage a CYA approach. I want to know the index lesions, where they are, their size, the findings on T2WI (T2-weighted imaging), DWI (diffusion weighted imaging) with the apparent diffusion coefficient (ADC) values given, and 3. When contrast is used I want to know which Gadolinium (Gd)-based contrast agent (GBCA) is intended & to be sure it is one in the cyclic & ideally non-ionic category (e.g., Gadovist, ProHance) to minimize toxicity. 4. Of course I want a PI-RADS v2 score rendered. 5. In the best of worlds I would like to see snapshots of the area(s) of concern and have the radiologist label pathologic findings so that I and other medical oncologists become more educated about imaging in PC patients. 6. Lastly, urologists should always defer prostate biopsies until at least 6 weeks after or during the mp-MRI since hemorrhage invariably occurs and results in a more problematic interpretation. These are some issues important to me in my care of PC patients. Stephen B. Strum, MD, FACP

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