A phase I clinic trial has revealed median survival after a new gene therapy was 14.4 months, compared with eight months typically seen in patients with high-grade glioma (stock photo)
Minnesota, US (BBN) - A new form of gene therapy has shown promise in battling a type of deadly brain cancer.
More than a quarter of people with recurrent high-grade glioma – the most common type of adult brain tumor – were still alive three years after the pioneering treatment, reports Daily Mail.
Median survival among clinic trial participants was 14.4 months, compared with eight months typically seen in patients.
Experts say the new treatment is safe, because while it uses high concentrations of chemotherapy, it spares sufferers from systemic exposure to its harmful effects.
Around 160,000 people are diagnosed with high-grade – or fast-growing – gliomas worldwide each year, and it is the type of tumor US Senator John McCain was diagnosed with earlier this year.
They recur in most patients and for many the disease cannot be cured.
GLIOMA TUMORS
Glioma is a broad category of brain and spinal cord tumors that come from glial cells, brain cells that can develop into tumors.
The symptoms, prognosis, and treatment of a malignant glioma depend on the person’s age, the exact type of tumor, and the location of the tumor within the brain.
They are often diagnosed in the 4th through 6th decade of life, depending on the type of glioma.
Low-grade (slow-growing) versions of gliomas can occur in children. Brain tumors are slightly more likely to occur in males.
Prior radiation to the brain is a risk factor for malignant gliomas. Some genetic disorders also increase the risk of development of these tumors in children but rarely in adults.
There are no lifestyle risk factors associated with malignant gliomas. This includes alcohol, cigarette smoking, or cell phone use.
Gliomas are tumors of the glial tissue, which hold and support nerve cells and fibres.
They tend to grow and infiltrate into the normal brain tissue, which makes surgical removal very difficult – or sometimes impossible – and complicates treatment.
'Given the deadly nature of this disease, three-year survival is rarely reported in the recurrent setting,' said study author Dr Clark Chen, head of the department of neurosurgery at the University of Minnesota Medical School.
'It is notable that the survival benefit was seen across a range of patients, and not just limited to patients with specific genetic mutations.
'This finding indicates that many patients could benefit from this treatment.'
KEY FINDINGS
The phase 1 trial included 56 patients with the disease.
The treatment tested delivers local chemotherapy specifically to the brain tumor.
It uses Toca 511 and Toca FC, a combination drug involving a gene therapy agent and a prodrug, a biologically inactive compound which can be metabolized in the body to produce a drug.
'Toca 511 and Toca FC work together to turn the brain tumor into a factory that produces an anti-cancer drug while also activating the immune system through a combination of mechanisms, which together work to attack the cancer,' Dr Chen explained.
Patients were first injected with Toca 511, a replicating virus that only infects actively dividing tumor cells.
Once inside the cancer cell, the virus delivers a gene for an enzyme called cytosine deaminase (CD).
'As the virus replicates and spreads to other cancer cells, it programs them to make CD. Next, patients received a pill, Toca FC, which is an inert compound.
'Once inside the cancer cell, CD converts Toca FC into the anti-cancer drug 5-fluorouracil, which kills the cancer cell,' the researchers explained.
'This treatment has a very favorable safety profile,' said Dr Chen.
'The Toca 511 therapy approach spares the body from exposure to systemic chemotherapy, while creating high concentrations of chemotherapy in the tumor cells and their microenvironment.'
The results of the study, which was sponsored by therapy maker Tocagen, were presented at the International Conference on Molecular Targets and Cancer Therapeutics, in Philadelphia.
Research presented at medical conferences are considered preliminary until it is published in a peer-reviewed medical journal.
BBN/MMI/ANS