Nick Mulcahy

May 20, 2015

NEW ORLEANS — The much ballyhooed multiparametric (mp) MRI does not appear to be suited as stand-alone test for diagnosing prostate cancer after an elevated PSA, according to new research.

The expensive and powerful technology failed to identify 16% of men with high-grade cancer (Gleason score ≥7) in a prospective study of 1044 men with an elevated PSA.

Thus, men with an elevated PSA should consider a prostate biopsy even if an mpMRI appears normal, concluded the authors, led by Christopher Filson, MD, of UCLA.

"More and more clinicians are incorporating multi-parametric MRI in the work-up of patients with concerns about a diagnosis of prostate cancer," said Dr Filson at a press briefing at the annual meeting of the American Urological Association, where the study was presented.

Increasingly, MRI is being used initially instead of a traditional 12-core needle biopsy, he added.

This obviously raises the question of its suitability as a stand-alone test, said Dr Filson, whose new study was provocatively titled, "Should a Normal Multi-parametric MRI Preclude Prostate Biopsy?"

To address the issue, Dr Filson and colleagues sought to determine — for the first time — the negative predictive value of mpMRI. So, they looked at the results of "systematic mapping biopsy" (ie, ultrasound-guided needle biopsy) in 241 of the men in the study who showed no suspicious lesions on the initial mpMRI.

Notably, 75 additional patients who also had no "region of interest" on mpMRI (31%) were found to have a Gleason score 6 or low-grade prostate cancer. This finding was more likely in patients with smaller prostates and those with prior positive biopsies.

Thus 47% had some kind of prostate cancer detected despite the initial negative mpMRI finding. This means that 53% of the cohort had a true negative (ie, both the mpMRI and the needle biopsy were negative).

This translated into a negative predictive value of mpMRI for Gleason score 6 and Gleason score > 7 of 53% and 84% respectively.

"It's still not 100% accurate," said Scott Eggener, MD, from the University of Chicago in Illinois, who moderated the press briefing.

"We are nowhere close to making MRI the standard of care," added Dr Filson. Much more investigation is need into its capabilities, he added.

However, Dr Eggener pointed out that MRI is better than needle biopsy alone for detecting the prostate cancers that are clinically significant and more likely in need of treatment.

"MRI is very useful and is more accurate [than needle biopsy] for identifying Gleason 7 or higher cancers," he observed.

Needle biopsies miss about 15% to 20% of all prostate cancers, commented Dr Filson.

The men in the study had an average age of 64.7 years and a median PSA of 4.9 ng/mL. Among the 244 patients who had an MRI with no signs of disease, 74 were undergoing their first biopsy, 54 had 1 prior negative biopsies, and 116 had a prior positive biopsy. Biopsy sites were identified and sampled by a single operator using the Artemis system for guidance.

Funded by the Beckman Coulter Foundation, Jean Perkins Foundation, Steven Gordon Family Foundation, and Urology Care Foundation Research Scholars Program.

Dr Eggener disclosed financial ties to Janssen Pharmaceuticals, Myriad Genetics, NxThera, and Profound Medical. Dr Filson disclosed no relevant financial relationships.

American Urological Association (AUA) 2105 Annual Meeting: Abstract MP60-11. Presented May 18, 2015.

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