[Chemotherapy of brain tumors]

Despite recent attempts to improve chemotherapeutic approaches for the treatment of malignant gliomas, results remain limited and palliative. The development of effective chemotherapy for tumors of the central nervous system (CNS) is complicated in that the blood-brain barrier (B.B.B.) hampers the penetration of most drugs into the brain and cerebrospinal fluid. The factors governing delivery in the brain are the drug's molecular weight, lipophilicity and degree of ionization. Now the standard therapy for malignant glioma is maximal tumor resection followed by combination radiotherapy plus chemotherapy. Nitrosoureas are representative drugs which easily cross the B.B.B.. It has been shown that nitrosourea compounds have an additive effect to radiotherapy. The toxicity profile of nitrosoureas is leukocytopenia and thrombocytopenia as a dose-limiting factor. Furthermore, the great heterogeneity of malignant glioma tissues offered a rationale for the use of multiple drugs. Many studies were reported to show a substantial advantage for the multidrug regimen over control series utilizing single drugs alone. Despite clear examples of the effectiveness of chemotherapy, we are still far from improving the cure rate for the vast majority of patients with primary malignancies of the CNS. Further improvement in patient survival may depend upon understanding and manipulating the pathways that regulate aberrant growth in these tumors. The development of new anticancer agents, which are sensitive to malignant glioma and can reach a high concentration in glioma tissue, is warranted.