New imaging technique helps detect brain tumours earlier

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.