A trial of a potential new brain cancer treatment has shown that a virus injected directly into the bloodstream can reach tumours deep inside the brain and switch on the body's own defence system to attack them.
The trial involved just nine patients, but scientists said that if the results could be replicated in larger studies, the naturally occurring 'reovirus' could be developed into an effective immunotherapy for people with aggressive brain tumours.
"This is the first time it has been shown that a therapeutic virus is able to pass through the brain-blood barrier," said Adel Samson, a medical oncologist at the University of Leeds' Institute of Cancer and Pathology who co-led the work.
He said their trial had shown not only that a virus could be delivered to a tumour deep in the brain, but that when it reached its target, "it stimulated the body's own immune defences to attack the cancer".
Published in the journal Science Translational Medicine on Wednesday, the trial involved nine patients with tumours that had either spread to the brain from other areas or were fast-growing gliomas, an aggressive type of brain cancer.
All the patients were due to have their tumours removed surgically, but in the days beforehand they were each given a single dose of the reovirus administered via intravenous drip into the bloodstream.
Once the tumours were removed, the scientists analysed samples to see if the virus had been able to reach the cancer, which in some cases was deep within the brain.
In all nine patients, there was evidence that the virus had reached its target, they said. There were also signs that the replicating virus had stimulated the immune system, with white blood cells or so-called "killer" T-cells being drawn to the tumour to attack it.
Alan Melcher of Britain's Institute of Cancer Research, who also co-led the study, said the results pointed a way forward for more trials using this virus, including testing whether it can harness the immune system to super-charge the effect of existing chemotherapy and radiotherapy treatments.
"Now we know we can get reovirus across the blood-brain barrier, we have begun clinical studies to see just how effective this viral immunotherapy can be," he said.
