Diffusion-weighted MRI shows promise in detecting advancing prostate cancer

24 Jan 2011

An advanced type of magnetic resonance imaging — diffusion weighted MRI — could be used instead of an invasive biopsy to decide whether prostate cancer patients under active surveillance need treatment.

The results of a pilot study conducted by The Institute of Cancer Research (ICR) and The Royal Marsden Hospital to investigate the technique were published in The British Journal of Radiology last month.

Some prostate cancers can be aggressive while others never require treatment. Men diagnosed with early stage prostate cancer therefore have the option of delaying therapy and opting instead for Active Surveillance — regular monitoring by biopsy and testing levels of prostate specific antigen (PSA) in the blood. However, biopsies are invasive and carry side-effects while PSA testing can be inaccurate, so scientists are looking for other ways to monitor cancer growth in these men and determine if treatment is needed.

An accurate test is particularly important as recent figures show the proportion of men who opted for Active Surveillance increased from zero to 39% between 2002 and 2006, and has likely become more common since NICE made it a standard treatment option in 2008*.

Scientists at The Institute of Cancer Research (ICR) and The Royal Marsden Hospital used a technique called diffusion-weighted MRI to scan 50 patients at their initial prostate cancer diagnosis and at a follow-up appointment an average of two years later.

Each scan was then used to calculate a figure called an Apparent Diffusion Coefficient, a measurement of water movement within tissue. The team had previously shown that these measurements are significantly lower in patients with high-risk tumours, but this is the first time they have been calculated for men under Active Surveillance.

By their follow-up appointment, 17 men had required treatment as their cancer had progressed, while 33 men remained under Active Surveillance. The team found that diffusion-weighted measurements fell between the two scans in men who progressed to treatment, but remained similar for men still under Active Surveillance.

“Diffusion-weighted MRI has a lot of potential for monitoring patients under Active Surveillance, as the scans clearly showed which men’s cancers were progressing,” says study leader Professor Nandita deSouza, Co-director of the Cancer Research UK and EPSRC Cancer Imaging Centre at the ICR. “If the technique continues to show promise in larger-scale studies, it could one day save men under Active Surveillance from the discomfort and potential complications of regular biopsies.”

Dr Lesley Walker, director of cancer information at Cancer Research UK, said: “It’s important that we find better ways to distinguish prostate cancers that spread quickly and which could be fatal from those that may not even need treatment. Imaging like this has great potential to provide non-invasive, accurate ways to monitor patients to help doctors limit the number of men who undergo unnecessary treatment. It now needs to be confirmed in much larger studies before this test should be used routinely in a clinical setting.”


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