Ketogenic diet has shown auxiliary effect on treatment of malignant tumors require high glucose consumption. This study is designed to evaluate the safety and efficacy of ketogenic diet adjunctive to high dose methotrexate(HD-MTX) chemotherapy for primary central nervous system lymphoma (PCNSL).

In a pilot study of primary central nervous system(CNS) lymphoma patients, ketogenic diet was given in adjunction with standard HD-MTX chemotherapy as interventional group; standard HD-MTX is given with routine diet as control group. The primary endpoint is the safety of ketogenic diet in PCNSL patients receiving chemotherapy, secondary endpoints include rate of complete remission, remission time, rate of tumor relapse and overall survival.

Inclusion Criteria:

1. Age 18-70
2. Histopathologically confirmed PCNSL
3. No systemic involvement
4. Ability and willingness to sign informed consent
5. Normal liver and kidney function
6. Karnofsky Performance Score of 60 or more

Exclusion Criteria:

1. Any systemic involvement of the tumor
2. Systemic illness or medical condition may pose additional risk, including cardiac, metabolic or endocrine disorders; incompensated renal or liver disfunction; history of renal calculi, hyperuricemia, hyper calcemia, mitochondrial disease, known disorder of fatty acid metabolism, porphyria, carnitine deficiency and pancreatitis
3. Uncontrolled hyperlipidemia or hyperglycemia
4. Human immunodeficiency virus positive, or hepatitis C positive
5. Pregnancy of breastfeeding
6. Inability or unwillingness to give written informed consent.