RSNA: MRI could play larger role in fighting prostate cancer

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CHICAGO—In the era of the prostate-specific antigen (PSA) screening, imaging has played a supporting role in combating prostate cancer, though that could be changing as the use of prostate MRI becomes more common, according to a presentation on Nov. 28 at the 97th Scientific Assembly and Annual Meeting of the Radiology Society of North America (RSNA).

The key issue, according to Peter L. Choyke, MD, of the molecular imaging program at the National Cancer Institute, is overtreatment. PSA tests are cheap and widely used, yet the reduction in mortality is uncertain. Overall mortality has been remained fairly steady while the number of diagnoses has doubled since the mid-1970s. That doesn’t paint the whole picture, though, as taking a closer look at the numbers reveals that age-adjusted mortality for prostate cancer in men over 65 is declining.

On the flip side of the overtreatment problem, many cancers are not effectively treated and prostate cancer is the number two cause of cancer death.

“Prostate cancer is a diverse disease. It has a wide range of aggressiveness from very indolent to rapidly fatal and the majority of the screening lesions will be low-grade. We will have to treat enormous numbers of men to save one life,” said Choyke, adding that under current practices, about 48 men are treated to save one life.

“Notwithstanding that, many lesions are discovered too late for cure,” he said. “So we overtreat indolent disease, we undertreat aggressive disease. We need to match the right therapy to the right patient and that’s where personalized medicine or imaging will find an important role.”

Current treatment strategies rely on information from a nomogram, which combines results from a PSA test, a patient’s Gleason score and anatomic staging, but Choyke said imaging data should be included in the mix.

Among the modalities, prostate MRI is unparalleled in diagnosing prostate cancer, said Choyke, especially with the combination of diffusion waving, dynamic contrast enhancement and MR spectroscopy. MRI can guide biopsies and may help differentiate between indolent and aggressive disease. It might also lead to image guidance of organ-sparing focal therapies.

Choyke said that there are multiple opinions on when to use imaging to diagnose prostate cancer, but a growing number of men are asking for imaging even before biopsy.

Co-presenter Masoom Haider, MD, of the University of Toronto, said that in the U.S. National Comprehensive Cancer Network guidelines barely mention the use of MRI for diagnosing prostate cancer, and that’s in the context of local recurrence after radiation therapy. In Canada, there are no specific guidelines or prohibitions on the use of MRI, but this has led to long waits for patients.

Haider said the most progressive guidelines for the use of MRI come from The Netherlands, where potential use of MRI is part of the strategy for intermediate to high-risk prostate cancer patients and is used for staging repeat biopsies and for the localization of carcinoma for therapy.

As more evidence-based trials are conducted, they will advance the case for the expanded use of MRI in prostate cancer treatment, said Haider.