Fasting makes brain tumors more vulnerable to radiation therapy

Prior work by USC professor of gerontology and biological sciences Valter Longo, corresponding author on the study and director of the Longevity Institute at the USC Davis School of Gerontology, has shown that short-term fasting protects healthy cells while leaving cancer cells vulnerable to the toxic effects of chemotherapy.

The latest study, which appears in the online journal PLoS ONE, is the first to show that periods of fasting appear to have the same augmenting effect on radiation therapy in treating gliomas, the most commonly diagnosed brain tumor. Gliomas have a median survival of less than two years.

"With our initial research on chemotherapy, we looked at how to protect patients against toxicity. With this research on radiation, we're asking, what are the conditions that make cancer most susceptible to treatment? How can we replicate the conditions that are least hospitable to cancer?" Longo said.

Longo and his co-investigators, including Thomas Chen, co-director of the USC Norris neuro-oncology program, studied the combination of fasting with radiation therapy and with the chemotherapy drug Temozolomide, currently the standard treatment for the treatment of brain tumors in adults after an attempt at surgical removal.

The researchers found that controlled short-term fasting in mice, no more than 48 hours each cycle, improved the effectiveness of radiation and chemotherapy in treating gliomas. Despite the extremely aggressive growth of the type of brain tumor studied, more than twice as many mice that fasted and received radiation therapy survived to the end of the trial period than survived with radiation alone or fasting alone.

"The results demonstrate the beneficial role of fasting in gliomas and their treatment with standard chemotherapy and radiotherapy," the researchers wrote. They said the results indicated the benefits of short-term, controlled fasting for humans receiving treatment for brain tumors.

Longo cautioned that patients should consult with their oncologist before undertaking any fasting: "You want to balance the risks. You have to do it right. But if the conditions are such that you've run out of options, short-term fasting may represent an important possibility for patients."

USC Norris Cancer Center, Mayo Clinic and Leiden University Hospital are all conducting clinical trials on fasting and chemotherapy. A clinical trial on glioma, fasting and radiotherapy is being considered at USC.

Fernando Safdie of the USC Andrus Gerontology Center and Sebastian Brandhorst of Centre for Medical Biotechnology, Germany, were co-lead authors of the study. Min Wei, Changhan Lee and Saewon Hwang of the USC Andrus Gerontology Center; Weijun Wang and Chen of the USC Norris neuro-oncology program at the Keck School of Medicine of USC; and Peter Conti of the Molecular Imaging Center at the Keck School were co-authors of the study.

The research was funded by the National Institutes of Aging in the National Institute of Health (grants numbers: AG20642 and AG025135), the Bakewell Foundation, the V Foundation for Cancer Research and a USC Norris Cancer Center pilot grant.