Different Treatment Strategies for Pediatric Brain Tumors
Malignant brain tumors are characterized by high local aggressiveness and tendency to metastasize within the central nervous system (CNS), and rarely outside it. Surgical approach represented and still represents the mainstay of treatment strategies. However, in the majority of cases, gross total resection is recommended to achieve long event-free survival and eventually the cure. In recent years neoadjuvant chemotherapy and adjuvant post-surgical radiotherapy and chemotherapy have gained relevance in facilitating complete surgical removal and in achieving and consolidating complete remission of such tumors. Post-surgical radiation therapy still represents the basic adjuvant treatment for children over three years with standard risk, non metastatic medulloblastoma. This approach is also considered a very important tool for children affected by ependymoma. However, associated chemotherapy is also needed when reduced doses of radiation therapy are administered, in cases of tumors characterized by a more aggressive biologic behaviour, such as high grade gliomas, and metastatic tumors of any origins. The majority of CNS tumors are of neuroepithelial origin and as such responsive to many antineoplastic drugs, like alkylating agents, antimetabolites, and alkaloids. However, in order to reach tumor cells inside the CNS these drugs have to overcome the blood brain barrier. A number of interesting tools able to disrupt or bypass the barrier, such as ionizing radiations, osmotic procedures or the liposomal technology applied to antiblastic drugs, exists. Starting from a dose of radiation of 30 Gy the permeability of an irradiated area is significantly increased compared to that of the unirradiated surrounding cerebral tissue. Many present treatment regimens include concurrent radiotherapy and chemotherapy in the post-surgical phase, and encouraging results have been reported. In the future better results will certainly come from modern technologies applied to radiation therapy, such as tomo-therapy, and from discovery of new drugs or alternative methods of administration of conventional ones.
Keywords: Brain tumors, chemotherapy, concomitant chemoradiotherapy, neoadjuvant, adjuvant, iposomes, anthracyclines, neuronavigation, diffusion-weighted imaging, diffusion tensor imaging
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