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

September 1, 2017

Magnetic resonance imaging (MRI) of the prostate may be used in many clinical scenarios, including primary screening, active surveillance, and in patients with a previous negative biopsy and rising PSA. In this interview, Scott Eggener, MD, explains whether MRI is warranted in each of these situations and the benefits and challenges this technology presents.

Scott Eggener, MDMagnetic resonance imaging (MRI) of the prostate may be used in many clinical scenarios, including primary screening, active surveillance, and in patients with a previous negative biopsy and rising PSA. In this interview, Scott Eggener, MD, explains whether MRI is warranted in each of these situations and the benefits and challenges this technology presents. Dr. Eggener is associate professor of urology and director of the Prostate Cancer Program at the University of Chicago. Dr. Eggener was interviewed by Urology Times Editorial Consultant J. Brantley Thrasher, MD, professor of urology at the University of Kansas Medical Center, Kansas City.

 

Please tell us what you consider a quality MRI of the prostate.

That’s a very important question. There’s a wide variety of methods on how MRI is done. The single most important thing at an individual center is to have a meaningful discussion with the radiology team and a radiologist who has a specific interest in developing a prostate MRI program so they can gain experience and expertise. As you and the readers know, there are 1.5 Tesla magnets, 3 Tesla magnets, endorectal coils, and body phased array coils.

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In general, most of the data suggest a 3 Tesla magnet with an endorectal coil gives the best pictures and the most accurate information. However, not every center has a 3 Tesla magnet, and a lot of centers do without the endorectal coil for patient comfort and workflow. You have to decide at your center what is best for your patient population, knowing that you may not have the highest level magnet. We tend to use endorectal coils because our best prostate radiologist swears by them and believes they provide higher quality pictures. Patients are forewarned that the endorectal coil will be used.

 

Do you do these in a radiology suite or in the urology suite?

All of the MRIs are conducted in the radiology suite. The prostate biopsies are done in the urology clinic.

 

Where do you see the value of MRI of the prostate?

Undeniably, the load of research suggests MRI images provide additional information for specific men at risk for prostate cancer or already diagnosed with prostate cancer. But I think it’s critically important for patients and urologists to realize that MRI is not perfect and will give false-negative and false-positive results. We can’t take the MRI information as gospel in every patient. It’s a guide for identifying potential cancers, where extra samples from certain areas may help us make smart decisions.

Next: "I do not think it’s good-quality care right now for every man going for his first biopsy to have an MRI beforehand"

 

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

 

 

Let’s talk about active surveillance. How do you use MRI there?

There are two separate scenarios with active surveillance. The data are strong that in men who are considering active surveillance, MRI prior to the restaging biopsy helps better identify areas with higher grade cancers while effectively providing more information on whether surveillance is a smart idea. That’s done fairly routinely at our center and many others.

Also see: Factors in prostate Ca decision-making vary by race

However, once men are on active surveillance, it is not standard of care to routinely obtain MRIs as part of their surveillance, and the NCCN guidelines specifically state that. However, emerging data from a few centers such as Memorial Sloan Kettering Cancer Center, the National Cancer Institute, and UCLA suggest that, while a man is on surveillance, an MRI periodically is very helpful in identifying whether he is “progressing.”

 

At our center, we use it in a patient who is on active surveillance, has low-volume Gleason 6 disease, and PSA below 10.0 ng/mL. Instead of doing an immediate 3-month re-confirmation biopsy, we do the MRI then. Does that sound reasonable?

That’s very similar to the practice pattern at our place, except we also routinely add the re-staging biopsy.

 

When do you use MRI in a patient with previous negative biopsies whose PSAs are going up?

In many ways, I think that’s the sweet spot of prostate MRI. There is a large amount of supporting data in that setting. A consensus statement was published in 2016 by the Society of Abdominal Radiology in conjunction with the American Urological Association. The key take-home points are to talk to your team about having a quality MRI and what it takes to get there, and to have experienced people interpreting them. But if the patient has a PI-RADS 3 to 5 lesion, it should be sampled a minimum of two times per lesion, sometimes more, depending on its size. There are many different ways of getting a needle into that lesion, but the data on whether one technique is better than the other are not great.

There are three main techniques for conducting an MRI-guided prostate biopsy. First is called cognitive registration, which is basically seeing an abnormality in a particular region on MRI and conducting an ultrasound-guided biopsy to take extra samples from that area. Second is an in-bore MRI biopsy, which is very time-consuming but is probably the best way to confirm that your needle is inserted into the region of interest. Third, which seems to be the most commonly used and what we use, is done in the urology clinic using a platform that fuses the MRI image with the ultrasound image to take extra samples.

 

Talk a little about what a urologist needs to do to get up to speed in fusion biopsy. Would you agree it’s not just one in-service program?

I absolutely agree. There are courses and training sessions, but like most things we do, it takes time and thoughtful insight into looking at your own outcomes. At our center, we decided that one urologist would do all of the fusion biopsies. We’ve looked back at the biopsy data and have regular communication with our radiology team where we’ve correlated data with prostatectomy specimens. We think of it as an iterative process.

 

Early on, we had multiple radiologists who happened to be covering the MRI room, and that didn’t work out well for us. Would you agree that that team of a dedicated reader (radiologist) and dedicated surgeon (urologist) probably makes for the best systematic review of the MRIs, the best biopsy, and the best results overall?

Absolutely. There’s even published research confirming that. Memorial Sloan Kettering showed the same MRI images to three separate GU radiologists, and the accuracy varied among those three. Whether you’re in an academic practice or a community practice, it’s incredibly important to identify people who have a specific interest and skill set.

Next: What do you do with PI-RADS 3 or 2 lesions?

 

Are there courses that you recommend?

There are many courses available through radiology conferences and urology conferences, and I don’t have specifics on which is better than the other. At the AUA annual meeting in Boston, there was a line out the door for a course called “Prostate MR Imaging: What a Urologist Should Know.” There’s clearly interest and energy on the urologists’ part to enhance their skills.

 

What do you do with PI-RADS 3 or 2 lesions?

Currently we don’t take extra samples from PI-RADS 2 lesions. But standard of care nowadays and in the consensus guidelines is any PI-RADS 3 through 5 lesion deserves some extra attention, with a minimum of two samples from that area.

 

How do you handle the patient whom you’re concerned about but whose MRI is negative for PI-RADS 3, 4, and 5? Do you proceed with a saturation biopsy? Do you do anything differently in the clinical setting?

That’s a complex situation, and the good news and bad news is that a number of different strategies are available. There are the imaging biomarkers like MRI. There are many serum and urine biomarkers that can be helpful in that space. It really depends on your level of clinical concern. I think we underutilize some tools that are readily available to us such as a percent-free PSA or a prostate volume. Those are helpful in deciding whether to simply see this patient again in 6 months, utilize one of the more advanced biomarkers to help make a decision, or-if you are very concerned-do an extensive biopsy.

 

Is there anything else you would say to urologists pertinent to an MRI program?

I think it’s really important to recognize the things MRI is very good at and the things it’s not as good at. For instance, it is very good at identifying sizable lesions. It is very good at identifying most, but not all, high-grade lesions. However, the operating characteristics of finding microscopic extracapsular extension are not very good. Why is that relevant? It’s incredibly relevant because many men now get an MRI prior to their prostatectomy. It is not appropriate to take the MRI findings as gospel and plan your nerve-sparing surgery or your resection status based on that.

 

Do you use MRI at all to help formulate your operative approach?

I do, but it’s important to get into the nuances of it. I do not routinely obtain an MRI before every prostatectomy, although our center does have a pre-prostatectomy grant in which hundreds of men have gotten them. I think of the MRI before prostatectomy as a useful piece of information that gets integrated with everything else I already know about the patient to help make a smart decision before and during the surgery on whether to spare part or all of the nerves on a specific side.

What I don’t like to hear from colleagues is, “The MRI suggests extracapsular extension, so I’m definitely going wide on that side,” or “There’s no extracapsular extension on the MRI, so I’m going to aggressively nerve spare.” To my point, a published randomized trial from Europe looked at about 400 men randomized before prostatectomy to MRI versus no MRI. The primary endpoint was surgical margin status, and there was absolutely no difference between the two study arms.

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