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?