Application of stem cell transplant for brain tumors

Brain tumors are the second most common malignancy in children and the most common solid tumor. The majority of children are treated with surgery alone or in combination with radiation and/or chemotherapy. Recently investigators have used high dose chemotherapy with autologous stem cell rescue (ASCR) in patients with malignant brain tumors. This approach has been most successful in chemosensitive tumors including medulloblastoma, supratentorial primitive neuroectodermal tumors (SPNET) and central nervous system germ cell tumors (CNS GCT). In addition, the use of high dose chemotherapy has enabled the reduction and in many cases elimination of radiation therapy to very young children. To date there have been no prospective randomized studies comparing high dose chemotherapy and ASCR with conventional therapy. Radiation therapy is often not an option for patients with recurrent disease and conventional dose chemotherapy rarely if ever results in long-term survival. Unfortunately, the majority of studies using conventional therapy in order to delay irradiation in young children newly diagnosed with malignant brain tumors have been unsuccessful. Although the numbers are small, preliminary data suggest that not only is survival but also quality of life is superior with the use of high dose chemotherapy. Future studies will most likely include the use of new agents as part of the cytoreduction. In addition, through the use of peripheral blood stem cells and improvements in supportive care, multiple courses of high dose chemotherapy can be administered. High dose chemotherapy with ASCR is a foundation upon which many different types of therapies can be built. Several possibilities include the use of anti-angiogenesis agents, monoclonal antibodies and biologic response modifiers.