July 30, 2006
Gliomas are a particularly aggressive form of brain tumour
The venom is used as a carrier to deliver radioactive iodine into tumour cells left behind after surgery has removed the bulk of the tumour.
So far the technique has been tested in 18 patients and further trials are under way, a report in the Journal of Clinical Oncology says.
Initial findings suggest the treatment is well-tolerated and may be effective.
Gliomas can be a particularly aggressive form of brain tumours, with only 8% of patients surviving two years and 3% surviving five years from the time of diagnosis. Despite advances in surgery, radiotherapy and chemotherapy, there has been little improvement in length of survival for patients with gliomas.
Researchers at Cedars-Sinai Medical Center, in California, carried out a study using TM-601, a synthetic version of a peptide that naturally occurs in the venom of the giant yellow Israeli scorpion.
Unlike many substances, the peptide can pass through the bloodstream into the brain and can bind to glioma cells.
Patients in the study first had surgery to remove their tumour.
Then 14 to 28 days later, a single, low dose of TM-601 with radioactive iodine attached was injected into the cavity from which the tumour had been removed.
Six patients were given additional doses of the drug.
The main reason for the trial was to check tolerance of the dose and the researchers said there were very few adverse effects.
Median length of survival for all patients was 27 weeks, but two patients had no evidence of tumour and were still alive 33 and 35 months after surgery.
Analysis showed that most of the radioactivity delivered by the drug had disappeared after 24 hours.
Any radiation that was left was localised to the tumour cavity, suggesting the drug was binding to the tumour cells rather than normal brain cells.
The drug also binds to other types of tumours and the researchers are planning further studies.
Study leader Dr Adam Mamelak, a neurosurgeon at Cedars-Sinai Medical Center, said: "We're using TM-601 primarily as a carrier to transport radioactive iodine to glioma cells, although there are data to suggest that it may also slow down the growth of tumour cells.
"If studies continue to confirm this, we may be able to use it in conjunction with other treatments, such as chemotherapy, because there may be a synergistic effect."
Ed Yong, cancer information officer at Cancer Research UK, said: "Treating brain cancers with radioactive scorpion venom sounds like science fiction.
"But this preliminary study shows that this approach is safe and has potential. Now, larger trials are needed to work out how effective it is.
"This study highlights the varied and ingenious approaches that scientists are using to improve cancer treatments."