The researchers, led by Adrienne C. Scheck, from Barrow Neurological Institute at St. Joseph's Hospital and Medical Center in Phoenix, Arizona, in the US, reported the results of using the combination therapy on mice in PLoS ONE.
Theirs is thought to be the first study of its kind to look at the effects of the ketogenic diet with radiation.
In a press statement released this week, Scheck says their study shows promise for treating human malignant gliomas:
"We found that the ketogenic diet significantly enhances the anti-tumor effect of radiation, which suggests that it may be useful as an adjuvant to the current standard of care for the treatment of human malignant gliomas," she explains.
Ketogenic DietThe ketogenic diet is a high fat, low carbohydrate, controlled protein diet that has been used since the 1920s to treat epilepsy. The word ketogenic means the body produces ketones (keto = ketone, genic = producing).
Usually the body converts carbohydrates (from foods like sugar, bread, pasta) into glucose (a type of sugar) to use for energy. In the ketogenic diet, because of the restriction in carbohydrate intake, the body can't use glucose and is forced to use fats as its source of energy: a process known as "ketosis".
In a recent study, scientists showed it may be possible to use specific fatty acids from the ketogenic diet to make a pill, so epilepsy patients can have the benefit of the diet without its side effects, which include constipation, hypoglycaemia, retarded growth and bone fractures.
There is also evidence that the diet's effect on brain regulation or homeostasis has potential for treating other brain disorders.
Increased SurvivalFor their study, Scheck and colleagues used two groups of mice with high-level malignant gliomas. They kept one group on a standard diet and the other group on a ketogenic diet.
The ketogenic diet they used was KetoCal (KC) a nutritionally complete, commercially available formula used in the treatment of epilepsy in children. The formula has a 4:1 ratio of fat to carbohydrate plus protein.
Both groups received radiation therapy and regular brain scans to monitor tumor growth.
The results showed that the median survival for the mice on the ketogenic diet was about five days longer than the mice on the standard diet, and the vast majority of them survived with no sign of tumor recurrence, even when they switched back to a standard diet, for over 200 days.
None of the mice on the standard diet survived more than 33 days.
Adjuvant Therapy in Human Brain Tumor TreatmentThe authors conclude that the ketogenic formula "significantly enhances the anti-tumor effect of radiation".
They suggest the changes to cell metabolism induced through the diet may make it a useful "adjuvant to the current standard of care for the treatment of human malignant gliomas".
Speculating on the reason why the ketogenic diet is effective when combined with radiation therapy, they suggest it stops tumor growth by reducing the stimulation of growth factor hormones, and it may also reduce inflammation and edema around the tumors.
Sheck is currently planning to set up clinical trials in humans.
She says the diet could easily and quickly be incorporated as an adjuvant therapy in current human brain tumor treatments without having to seek approval from regulators.