Scans for diagnosis and staging - MRI-Magnetic Resonance Imaging

MRI Guided Biopsy to Find "Hidden" Prostate Tumors


Why do some men with elevated prostate specific antigen (PSA) levels who are carefully monitored and undergo repeated negative biopsies still develop aggressive prostate cancer? Clinical researchers at Princess Margaret Hospital (PMH) in Toronto, Canada believe they can now answer that baffling question.

The answer, they say, is hidden tumors located on the top of the prostate that evade traditional diagnostic procedures, including ultrasound-guided needle biopsy. The PMH research, published online today in the British Journal of Urology International (BJU 8938), demonstrates that magnetic resonance imaging (MRI) is the best tool to reveal such tumours.

"Our findings identify a specific high-risk group whose tumors are difficult to diagnose because of location. These men benefit from MRI, which guides the biopsy procedure with a high degree of accuracy," says author Dr. Nathan Lawrentschuk, Urologic Oncology Fellow, PMH Cancer Program, University Health Network. "The research team calls the clinical presentation of elevated PSA and repeated negative biopsy results in 'prostate evasive anterior tumor syndrome' (PEATS)."

MRI machine

This use of MRI is not foolproof but it is a significant advance. A team of urologists, surgeons, radiologists and pathologists studied 31 PMH patients who had positive biopsy results and tumors on top of their prostate as shown on MRI. They found that MRI was able to help diagnose hidden prostate tumors 87% of the time.

Dr. Lawrentschuk says clinicians need to be aware of PEATS because these hidden tumors can be aggressive.

Edited by J. Strax 10/08/09



Princess Margaret Hospital, Toronto, Canada is a member of University Health Network, which also includes Toronto General Hospital and Toronto Western Hospital. All three are research hospitals affiliated with the University of Toronto. Their research arm is Ontario Cancer Institute.

ABSTRACT of the publication

The role of magnetic resonance imaging in targeting prostate cancer in patients with previous negative biopsies and elevated prostate-specific antigen levels.

In the past 20 years, magnetic resonance imaging (MRI) has developed rapidly, along with the management of localized prostate cancer. We summarize current data on the efficacy of MRI for targeting cancer, compared with biopsies, in patients with previous negative prostate biopsies and persistently elevated prostate-specific antigen (PSA) levels. The key clinical question is how many men benefit by having had prostate cancer detected purely because of the MRI-targeted, as opposed to standard scheme, biopsies. We reviewed all available databases for prospective studies in patients having MRI and prostate biopsy with previous negative biopsies and persistently elevated PSA levels. Six studies fulfilled the selection criteria, with 215 patients in all; in these studies, the cancer-detection rate at repeat biopsy was 21-40%. For MRI or combined MRI/MR spectroscopy, the overall sensitivity for predicting positive biopsies was 57-100%, the specificity 44-96% and the accuracy 67-85%. In five studies, specific MRI-targeted biopsies and standard cores were taken, with a significant proportion (34/63, 54%) having cancer detected purely because of the MRI-targeted cores. The value of endorectal MRI and MR spectroscopy in patients with elevated PSA levels and previous negative biopsies to target peripheral zone tumours appears to be significant. Although more data obtained with current technologies are needed, published results to data are encouraging. A comparison study and cost-benefit analysis of MRI-targeted vs saturation biopsy in this group of patients would also be ideal, to delineate any advantages.

British Journal of Urology International website


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Scans for diagnosis and staging - MRI-Magnetic Resonance Imaging