Kate Johnson

May 19, 2011

May 19, 2011 (Montreal, Quebec) — Targeted prostate biopsies that use a fusion of multiparametric magnetic resonance imaging (MRI) and ultrasound can produce a significantly higher yield and might be a replacement for traditional systematic biopsies, according to the results of a study presented here at the International Society for Magnetic Resonance in Medicine 19th Annual Meeting and Exhibition.

MRI can identify cancer in more than half of men for whom the initial biopsy is negative, but direct MRI-guided biopsy is not universally available — even to radiologists, said lead investigator Daniel Margolis, MD, assistant professor of radiology and codirector of prostate magnetic resonance imaging at the David Geffen School of Medicine, University of California at Los Angeles.

The blending of ultrasound guidance with MRI targeting could bypass this problem and accelerate the adaptation of targeted biopsy, he said.

"Urologists less familiar with imaging guidance may benefit from this technology by expanding to a larger population base," he added.

The study enrolled 54 consecutive patients with an abnormal prostate on physical examination and abnormal prostate-specific antigen levels who underwent multiparametric MRI — a blend of diffusion-weighted MRI, dynamic contrast-enhanced MRI, and traditional T2-weighted MRI — to identify targets for biopsy.

Targets were chosen by an experienced uroradiologist on the basis of a decreased T2 signal, abnormal dynamic contrast-enhanced MRI, or apparent diffusion coefficient.

Special magnetic resonance/ultrasound fusion software (Artemis, Eigen) was used to perform transrectal ultrasound-guided biopsies of the targets; standard systematic biopsies were performed at the same time.

Multiparametric MRI identified 86 suspicious targets in 49 patients, of which 61 targets (40 patients) were biopsied on the basis of the high probability of cancer.

After the first 25 patients, parallax imaging was added to optimize target acquisition, said Dr. Margolis.

Overall, 14 of the 61 suspicious targets were positive (23%), but after parallax optimizing, 8 of 17 were (47%) were found to be positive, he said.

Of the samples from 652 systematic biopsies and 150 targeted biopsies, 38 (5.8%) and 26 (17%), respectively, were positive; the difference was not significant (P = .14), reported Dr. Margolis.

However, after parallax optimization, the difference in positive cores reached statistical significance; 7.1% of the systematic biopsy samples and 37% of the targeted biopsy samples were positive (P = .04).

"MRI–ultrasound fusion targets additional cancers, compared with systematic biopsies, and may replace systematic biopsies — resulting in fewer total biopsies, improved yield, and improved confidence for patients with a small amount of low-grade cancer who opt for active surveillance," said Dr. Margolis.

"We are hindered by our blindness in looking at prostate cancer," said Anwar Padhani, MB, BS, FRCP, FRCR, moderator of the session, who is honorary senior lecturer at University College, London, and consultant radiologist at the Paul Strickland Scanner Centre, Mount Vernon Cancer Centre, in Northwood, Middlesex, United Kingdom.

"Systematic biopsies are nontargeted and so lead to underestimates of tumor aggressiveness and tumor staging. The multiparametric approach is clearly the way to go if we are going to improve men's health in the future, he said.

Dr. Margolis and Dr. Padhani have disclosed no relevant financial relationships.

International Society for Magnetic Resonance in Medicine (ISMRM) 19th Annual Meeting and Exhibition: Abstract 52. Presented May 9, 2011.

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