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.”