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New imaging technique helps detect brain tumours earlier

June 07, 2011

New imaging technique helps detect brain tumours earlier

Hospital News

June 2011

By Christopher Needles

Brain tumours are often very difficult for doctors to find. Current imaging
techniques that find other types of cancer without difficulty still often can’t
easily find brain tumours. That means many patients are diagnosed with brain
cancer too late for successful treatment.

A team of Ontario researchers at the Centre for Addiction and Mental Health
(CAMH) in Toronto hopes to change this. They have developed a new technique that
can help doctors better find brain tumours earlier in their development. This
technique was discovered out of research on Alzheimer’s disease, a more typical
area of research for CAMH, and could vastly improve treatment options for
patients with brain cancer. The lab plans to begin phase one clinical trials
this autumn.

“In order to detect brain tumours, doctors can use a brain imaging technique
called Positron Emission Tomography or PET,” explains Dr. Neil Vasdev, Associate
Professor in the Department of Psychiatry at the University of Toronto, Senior
Scientist at the CAMH PET Centre in Toronto and lead researcher on the project.
“PET technology allows us to clearly see very small amounts of radioactive
compounds called radiotracers that we introduce into the body.”

Most doctors today use an existing radiotracer called FDG, or
fluorodeoxyglucose. FDG is injected into the patient, where it travels around
the body and builds up in tissues that quickly absorb glucose, including most
tumours. When doctors then scan the body with a PET scanner, tumours literally
light up on the scan, “tagging” only the cancerous tissue. This allows doctors
to see quite clearly what is otherwise invisible to the human eye.

Currently, FDG is used in more than 90 per cent of all PET scans for cancer.
But a major problem occurs when using FDG to find brain tumours: the brain also
quickly absorbs FDG. That means tumours end up looking very much the same as the
normal, healthy brain tissue around them on a PET scan. Small tumours in
particular are hard to see in the brain and often missed.

“Our laboratory has invented a completely new radiotracer based on a
naturally occuring plant sugar, known as scyllo-inositol. It is much better at
tagging brain tumours, because it is not taken up by normal brain tissues,”
Vasdev says. “We can use this radiotracer for the early detection of brain
tumors and for monitoring the return of cancers following surgical and
chemotherapeutic treatment.”

The new radiotracer is completely safe for humans, with no likely side
effects. The radioactivity from the radiotracer disappears naturally shortly
after the scan is done.

Vasdev’s lab is currently in the process of submitting a clinical trial
application to Health Canada. This would see the first human use of the
scyllo-inositol radiotracer in patients suffering from gliomas, a common type of
brain tumour.

While Vasdev’s lab at CAMH has led the research on developing this
radiotracer for brain tumours, his work is in fact part of a much larger
collaborative effort. This effort features a large, interdisciplinary group of
researchers from the University of Toronto, University Health Network, and
STTARR labs in Toronto that are working together to develop the project fully.

“I first got involved in this project by working with collaborators who
approached our lab to develop this radiotracer for Alzheimer’s disease. The
radiotracer did not penetrate the brain as expected. But we discovered by chance
with our colleagues in the Faculty of Pharmacy at the University of Toronto that
this radiotracer is excellent for tumour imaging,” Vasdev explains.

CAMH, as Canada’s largest mental health and addiction teaching hospital, has
not been heavily involved in cancer research until now. Yet CAMH’s PET imaging
facility is one of the most developed in Canada, with not one but two machines
called cyclotrons that can make radiotracers. Vasdev saw this collaboration as
an opportunity to use this equipment to begin also helping cancer patients.

The project has been funded in part by the Ontario Institute for Cancer
Research (OICR) through its One Millimetre Cancer Challenge program. This
program has challenged imaging researchers in Ontario to develop new imaging
technologies to better detect small tumours. Small tumours are easier to treat
because they are less developed and there is less likelihood they have spread to
other parts of the body.

With the radiotracer now heading into clinical trials, Vasdev is now most
excited about the legacy it has left behind – and the potential this legacy has
to improve diagnosis for even more patients. “By going through this process, the
infrastructure is now in place for us to rapidly advance other radiotracers for
patients suffering from other tumour types, including breast and prostate
cancers,” he says.

And the majority of OICR funding has been allocated to training highly
qualified personnel at the postdoctoral, graduate and undergraduate levels.
“These trainees represent the next generation of scientists to support nuclear
medicine and cancer imaging programs in Canada. They will support the discovery
of future cancer diagnostics and treatments.”

Vasdev recently accepted a position as Director of Radiochemistry at
Massachusetts General Hospital and Associate Professor at Harvard Medical School
in Boston. His current project will continue on in Toronto and he looks forward
to continuing his association with it as an Affiliate Scientist and Adjunct
Professor.

Christopher Needles is a Communications Officer at the Ontario Institute for
Cancer Research.

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