PMH clinicians map group at high risk for aggressive, 'hidden' prostate cancer

Clinical researchers at Princess Margaret Hospital (PMH) can now answer the question that baffles many clinicians -- 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?

The answer is hidden tumours 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 tumours 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 tumour syndrome' (PEATS)."

"Knowing about PEATS may also be important for men already on 'active surveillance' -- patients with slow-growing prostate cancer who are being regularly monitored through PSA testing and biopsy. Every man does not need an MRI, but knowing about PEATS will help us identify those who do," says principal investigator Dr. Neil Fleshner, Head of the Division of Urology, Princess Margaret Hospital, Professor of Surgery at University of Toronto, and Love Chair in Prostate Cancer Prevention Research.

A team of urologists, surgeons, radiologists and pathologists studied 31 PMH patients who had positive biopsy results and tumours on top of their prostate as shown on MRI. They found that MRI was able to help diagnose hidden prostate tumours 87% of the time.

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

About Princess Margaret Hospital

Princess Margaret Hospital and its research arm, Ontario Cancer Institute, have achieved an international reputation as global leaders in the fight against cancer. Princess Margaret Hospital 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. www.uhn.ca

October 8, 2009