The survival interval of patients with gliomas ranges between 12 to 15 months. Recent findings revealed that dietary interventions to reduce glucose and glycolytic pathways could have a therapeutic effect. Ketosis can be an effective therapy to extend the survival of patients with gliomas.

Gliomas are invasive and aggressive tumors, which derive from glial or stem cells, and after neoplastic transformation, acquire glial cell characteristics. Treatment of high-grade gliomas includes measures to relieve symptoms and eliminate or control the tumor. Surgery, radiation, and chemotherapy are the most common options. Recent findings revealed that dietary interventions to reduce glucose and glycolytic pathways could have a therapeutic effect. CKD is a restrictive therapeutic diet consisting of a 4:1 ratio of fat-to-CHO and protein. Fat provides up to 90% of the caloric intake, while overall CHO intake is less than 50 g/day. CKD reducing blood glucose levels and increasing ketone body levels stimulates biochemical changes to achieve systemic ketosis. Though, evidence for CKD in clinical practice is still limited. This study focuses on the classic ketogenic diet (CKD), adjusted for each patient's energy needs by dieticians to achieve ketosis. The primary outcome is to assess the efficacy of CKD to extend the survival of patients with high-grade gliomas and brain metastases. Historical controls will be used to compare the outcome measurements.

Inclusion Criteria:

• Age 18-80
• Karnofsky Performance Score of 50 or more.
• Newly diagnosed, histologically confirmed glioblastoma grade 4, or secondary metastases or progression after surgical resection, radiation and chemotherapy.
• Normal function of liver and kidneys
• Ability to sign informed consent form

Exclusion Criteria:

• Diabetes mellitus
• Life expectancy >3 months
• Inability to adhere to diet
• Inability to give informed consent form
• Cholecystectomy last 1 year (before the study entry)
• Diagnosis of genetic disorder of fat metabolism