Multiparametric MRI Could Reduce Overdetection and Overtreatment in Prostate Cancer

Samir Taneja, MD

The use of multiparametric MRI in diagnosing and treating prostate cancer was explored in November during a continuing medical education course offered at the annual meeting of LUGPA. Urologist Samir Taneja, MD, summarized the pioneering application of the technique by his institution, the NYU Langone Medical Center, where about 850 MRI-targeted biopsies have been conducted over the past two years.

Taneja, a professor of Urology and Radiology and director of the Division of Urologic Oncology at the medical center, sat down with Urologists in Cancer Care to discuss the center’s use of the technology and how it might eventually be applicable in community practice.

Urologists in Cancer Care: What is multiparametric MRI, and how can it guide urologists in diagnosing and treating their patients with suspected or confirmed prostate cancer?

Taneja: In the field of prostate cancer, the typical paradigm for detection has been to do a PSA [prostate-specific antigen] test and, if abnormal, to start with a prostate biopsy. As a field, we’ve been heavily criticized because, many times, we find cancers that are slow-growing or are unlikely to cause death.

As a result, we end up treating—and generating secondary side effects in—patients who wouldn’t have died had their disease remained undetected. We refer to this as overtreatment. Part of what fuels the idea of overtreatment is overdetection, finding cancers randomly during biopsy that are probably unrelated to PSA elevation. We’ve felt that a major cause of overdetection in clinical practice is the way we do the biopsy, which is a random sampling of the gland. For the past several years, we’ve tried to determine whether imaging the prostate through a technique called multiparametric MRI can help us to sample in a more targeted fashion, and whether that can allow us to do a better biopsy.

The MRI is done in several sequences. The first is a traditional anatomic sequence that allows us to take a picture of the gland. The second and third sequences look at functional attributes of the prostate—in particular, blood flow. That’s what we call dynamic contrast enhancement. The MRI might also look at water movement: That’s what we call diffusion-weighted imaging. Using those sequences together increases the accuracy of the MRI and reduces the number of false positives.

In the prostate cancer arena, which patients may benefit from the use of multiparametric MRI?

We’ve advocated the use of MRI, as a routine, prior to biopsy in three categories of men at NYU.

In the first group, men who have never been biopsied before, the MRI might help us to avoid false negatives. If we’re sampling the most suspicious area of the prostate, it’s very unlikely we’ll miss a cancer, and if there is a cancer there, we’ll get a better sample of it. So now we can be more confident that the findings of the biopsy are actually representative of the aggressiveness of the disease, and we can counsel the patient better regarding whether or not he needs treatment. In addition, a lot of the data we’ve produced show that, at a certain suspicion level on the MRI, it’s very unlikely the man has aggressive cancer, so we think the MRI could be a tool for avoiding biopsy in a large number of men. In the second group, the fellows who have had multiple biopsies or even one negative biopsy but their PSA keeps rising, the biggest benefit of the MRI is that it probably reduces the number of repeat biopsies.

We published a paper recently in the Journal of Urology which shows that, in the days before we were doing MRI, if a man was chosen for a repeat biopsy, there was a one in three chance that he would end up with four repeat biopsies, and a one in seven chance that he would end up with five biopsies. That problem arises from this random sampling effect: You keep sampling until you find something.

Early intervention with MRI can reduce that repetitive biopsy cycle, a great benefit in terms of cost reduction and patient quality of life. We’ve also shown that the MRI in that setting more reliably allows us to find high-grade or aggressive cancers than the random biopsy technique.

Finally, in the surveillance patient, traditionally we’ve rebiopsied men annually because we worry they have more aggressive disease than what their original biopsy showed. With the MRI, we can do one repeat biopsy and determine who has high-risk disease and who doesn’t. In fact, at NYU, our survival protocol now is one repeat biopsy and then follow-up with MRI alone.

How might the use of this technology eventually affect guidelines for PSA testing?

Recent recommendations by the United States Preventive Services Task Force and other groups have all focused on the fact that, when we screen populations, we do seem to reduce mortality, but it comes at the tremendous cost of identifying a lot of cancers that would have been nonlethal. The general consensus of these task forces has been that the solution is to just stop PSA testing, accepting that a certain number of men will die from the disease in order for us to avoid overdetection.

The MRI can present a middle ground for trying to resolve overdetection without simply doing away with the PSA test. It can do that by selectively allowing us to decide who should or should not be biopsied or treated.

This conflict really arises from a difference in perspective. As somebody who has to go into an exam room, speak to a patient and explain to him that he’s at risk of dying of the disease, but ultimately tell him we shouldn’t do the test because it doesn’t benefit a population, there’s a tremendous disconnect.

In the aftermath of the USPSTF recommendations, what we’ve seen is mass confusion: confusion in the public, confusion among physicians. It’s changed screening practices in some states and not changed them at all in others. So this is a means by which we can add logical conclusions, logical methods to addressing the over-detection problem.

Is multiparametric MRI available yet in the community setting, and what are the challenges involved with its implementation?

Probably most community practices don’t yet have access. I would not advocate MRI of the prostate as a community standard, because in many settings it’s investigational. But it’s something to be explored.

There are several layers to integrating high-quality MRI into a clinical practice. The first is access to MRI scanners. The second would be providing good protocol and good-quality MRIs. Unlike a knee MRI, which is largely anatomic, this is a functional MRI, so the actual method by which the MRI is conducted is critically important. Next is the education of the radiologist. Learning to interpret the MRI is probably the most important hurdle for wide implementation in the community, because there’s a tremendous learning curve that goes with that, and there’s a lot of subjectivity. We find that, when we get MRIs from the community that are read as negative or positive, we’ll often disagree, maybe up to 50% of the time.

The next hurdle is getting radiologists and urologists to work together in some efficient systems approach. Everybody’s worried about their time efficiency in medicine; everybody’s worried where to put their attention. So communication and integration into healthcare systems is a big challenge for something like this.

The next is getting urologists to understand how to utilize MRI: who needs it, when would they use it, how would they target areas that are abnormal on the MRI?

And, finally, how do they interpret the data? What we want to be very careful of is that the enthusiasm over a new technique does not race ahead of the data that support it. There was recently an article about our work in the Wall Street Journal. That means every person in New York is reading about it. If now they come in saying they want it simply because it’s there, that could ultimately be a driver of overdetection, and it’s a real concern of mine. So what we want is to use it according to a very sound, evidence-based approach with the right goal in mind—and that is to reduce the overdetection problem in the United States.

How and when can more urologists in the community setting expect to have multiparametric MRI available?

For urologists who don’t have immediate access to an MRI, there are growing numbers of referral centers around the United States that do good-quality MRIs.

For urologists who want their own MRI, create partnerships with your local radiologist, come to centers of excellence, take courses, and start to integrate it in your own practice. We do training in the biopsies, and our radiologists do training in the imaging. Then, using your own practice, assess the outcomes. Don’t rely on my outcomes, rely on your own.

As time goes on, centers like mine, like UCLA and the NIH, where a lot of this work has been done, will have a growing body of data that tells us who benefits from an MRI and when it should be done. At that time, what I’d really like to see is that the community is ready to take it on, because they’ve already set the infrastructure in place.