A cannabis extract has been found to "drastically reduce" the size of brain tumours, researchers have said.
Scientists at St George's, University of London, were using tetrahydrocannabinol (THC) and cannabidiol (CBD) to research their effect on brain cancer.
Brain tumours are intrinsically difficult to treat and kill about 5,200 people every year. Survival rates are also poor, with just 10% of patients living for at least five years after diagnosis.
Researchers found that when TCH and CBD are used to treat brain cancers alongside radiotherapy, tumours can disappear.
Published in the journal Molecular Cancer Therapeutics, researchers found the most effective treatment was the combination of the chemical components of cannabis with irradiation.
In mice the treatment drastically slowed the growth of brain tumours when TCH/CBD was used with irradiation.
Wai Liu, lead researcher on the study, said: "The results are extremely exciting. The tumours were treated in a variety of ways, either with no treatment, the cannabinoids alone, and irradiation alone or with both the cannabinoids and irradiation at the same time.
"Those treated with both irradiation and the cannabinoids saw the most beneficial results and a drastic reduction in size. In some cases, the tumours effectively disappeared in the animals. This augurs well for further research in humans in the future. At the moment this is a mostly fatal disease.
"The benefits of the cannabis plant elements were known before but the drastic reduction of brain cancers if used with irradiation is something new and may well prove promising for patients who are in gravely serious situations with such cancers in the future."
Experts now hope to combine cannabinoids with current treatments in a human clinical trial.