Despite careful monitoring and repeated negative biopsies, some men with high levels of prostate specific antigen (PSA) still develop aggressive prostate cancer. Princess Margaret clinicians recently uncovered why: hidden tumours located on the top of the prostate that evade traditional diagnostic procedures, including ultrasound-guided needle biopsy. The PMH research, published online recently in the British Journal of Urology International, 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, UHN. "The research team calls the clinical presentation of elevated PSA and re­peated negative biopsy results '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 percent of the time.

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

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