Video: Prostate MRI: Should You Use Contrast? | Off The Cuff with Mark Moyad, MD, MPH
Off the Cuff with Mark Moyad, MD, MPH | Transcription
Dr. Moyad: If I want to get an MRI and someone says I can get one, just try to walk me through the process. You know, how long does it take? I gotta get a contrast. Is this something that is gonna be claustrophobic? I mean, if you were to walk someone through an MRI in terms of time, contrast, any of these basics that I want to know so I'm not scared going into it. Can you walk us through that?
Dr. Margolis: Yeah, so although the amount of time that you're at the imaging will be about an hour and a half, the amount of time you're in the scanner is about half an hour and about 25 minutes of that is scanning and 5 minutes is getting in and out of the scanner.
Dr. Moyad: Okay.
Dr. Margolis: Currently, we do use contrast because it helps us detect cancers and it helps us, to a small degree, classify them in terms of their overall risk. And so one reason why there's a lot of interest in getting away from the use of contrast, especially in resource-limited situations like, you know, countries that are developing or, you know, Kaiser or, you know, Canada where they really want to tamp down on the amount of resources they have as much as possible. It doesn't affect the suspicion that much, but I have seen that it does help with detection. So you see things much more distinctly on the dynamic contrast images and there are rare but common enough cases where the diffusion component and then we need dynamic contrast in order to make up for that. So, one thing that I suggest to my colleagues where they want to come up with a non-contrast, you know, accelerated a very abbreviated protocol—do the T2 and the diffusion-weighted imaging which are the other two components. You can get that all done within 15 minutes, and then look at the images and if you really need contrast, bring the patient back. You might think, can't you just do it while I'm on the scanner? You'd be on the scanner for another half an hour while we're trying to process all the data, transmit that to our work station, read the data, make that decision. So it's not efficient to do that while the patient is on the scanner.
Dr. Moyad: But what you're saying is, you don't always have to use contrast.
Dr. Margolis: Right.
Dr. Moyad: So I'm a patient walking in, at least now I know I'm 30 minutes in the scan. That's not too long. Easier said than done.
Dr. Margolis: Yeah, yeah.
Dr. Moyad: And do I bring that conversation up when I'm there? Do I really need contrast? I mean, how does that work for the patient?
Dr. Margolis: Right.
Dr. Moyad: Because I would assume they're going, they're just gonna give contrast in many cases if the patient doesn't bring it up.
Dr. Margolis: And they should because ultimately you want the best test. You don't want a test that maybe it's good enough, maybe it's not. And you don't want a test done by a radiologist who's used to the best test where you're getting some unusual version of it. So if you're in an environment where they do a lot of non-contrast examination. So my neighbors across the street, Sloan-Kettering, for follow up they do non-contrast. And, you know, far be it for me to criticize potentially the best cancer hospital in the world.
Dr. Moyad: If you want to, you should.
Dr. Margolis: But I think if you have the degree of expertise that my esteemed colleagues across the street have, that makes it a little easier. For most of us, and myself included, it's often enough, maybe even half the time, where having that contrast helps a little bit. Would I make a different assessment without it? Probably not, but it does help. And the risk to the contrast, as far as we can tell, is almost negligible. The main risk is allergy because some people will be allergic. And that, severe allergies occur in about 1 in 100,000 patients. So there's another concern that we now know that the gadolinium ion deposits in a portion of the brain called the basal ganglia.
Dr. Moyad: Yeah.
Dr. Margolis: And, you know, that's not normal and we can see it, and maybe that's not good. But as far as we can tell, in tens of millions of scans where we look at patients that have the exact same medical history and some got an MRI with contrast and some did not, there is absolutely no detectable difference in their neurological assessments. And so, although it does deposit it's maybe not a bad thing. As far as we can tell, it doesn't make any difference whatsoever.
Dr. Moyad: I think though what changed the game a little bit, and this is probably for another time, is that in December of 2017. I want to say December 19th, but I'll Google that and see if I'm right or wrong, the FDA came out and said, contrast, heads-up, we're not sure about it.
Dr. Margolis: Right.
Dr. Moyad: And then they produced a table of safer contrasts.
Dr. Margolis: Yes.
Dr. Moyad: And gadolinium came up there as a safer contrast, which is good, but so I don't know if you've had fall back from that 27 report—2017 report— where they said "Look out! We don't know what to say, but there might be a concern."
Dr. Margolis: There are two main classes of gadolinium-based contrast agents. The cyclic and the linear. And the cyclic is what we call a chelate or a molecule that binds the ion of gadolinium centrally, and so because it's in the middle it has a much stronger binding affinity, meaning that the likelihood that this little ion can escape and get into the basal ganglia is much smaller. Order of magnitude, like hundreds of thousands of times smaller. The linear compound still bind it very tightly. It's not just floating all-around your bloodstream, but we can measure the difference. And we've basically gotten away from all of the linear compounds except for two of them because they have a very specific different activity in the liver. So they're known as gadobinate and gadoxetate.
Dr. Moyad: God bless you.
Dr. Margolis: Thank you.
Dr. Moyad: Sorry, that was an easy joke, I had to throw that in.
Dr. Margolis: Fair enough.
But so we use when called gadobutrol, which is the trade name Gadavist. Better right?
Dr. Moyad: And that came up as a healthier one to use, right?
Dr. Margolis: Right.
So we know that it's safer in terms of it's less likely to disassociate from the chelate, meaning leak into the brain. But again, even with the cases where we do see it in the brain we think that it's probably completely safe. But we don't know, and that's the main concern that we have right now. So, is it worth the risk of getting contrast? Yes, because the risk of something bad happening from prostate cancer is something we can quantify. We can tell based on your PSA and your medical history what's the likelihood that you will have a bad event from prostate cancer. The likelihood that will occur from a gadolinium ion is so small that we can't measure it.
Dr. Moyad: So it's safe to say that you generally need the contrast and it would be smart to make sure that the contrast that your person is using is on the list of the better, safer contrasts. Right?
Dr. Margolis: Yeah, so it's a cyclic contrast agent.
Dr. Moyad: Cyclic contrast agent.
Dr. Margolis: Yep.