Methionine is an essential amino acid. Many solid tumors depend on the methionine that is taken in through the diet. The tumors need methionine to grow. A methionine free (or reduced) diet may help to shrink or slow the growth of some tumors. Temozolomide is a drug that is commonly used in the treatment of glioma. A methionine free (or reduced) diet may increase the effectiveness of temozolomide in the treatment of glioma.