Sorafenib in Children and Young Adults With Recurrent or Progressive Low-Grade Astrocytomas

Novel therapies are urgently needed for children with relapsed LGA who are not surgical candidates and/or have exhausted standard chemotherapy approaches. Although a vast number of "molecular targeted" agents have been developed over the past decade for the treatment of cancer, none have been evaluated for the treatment of LGAs. Recently, genetic alterations resulting in oncogenic BRAF have been identified to be highly prevalent in LGAs, providing a rational target for therapeutic intervention. The aims of this clinical trial are to estimate the efficacy, as well as safety and tolerability of sorafenib, a RAF and tyrosine kinase receptor inhibitor, in the treatment of pediatric patients with recurrent LGA. Sorafenib targets several pathways that, based on preliminary data from us and others, are likely contributing to the growth of LGAs: oncogenic BRAF, which is present in the majority of grade I LGAs and VEGFR2 and PDGFR, which are well-described mediators of tumor angiogenesis. Since sorafenib inhibits a number of additional kinases whose role in LGA growth has not yet been explored, it is possible that inhibition of pathways other than the primary targets may result in additional anti-tumor effects of sorafenib in LGA. Although the investigators hypothesize that LGAs with oncogenic BRAF should be most sensitive to sorafenib, the additional targets of sorafenib may also result in significant anti-tumor effects in LGAs with wild-type BRAF. Therefore, the investigators propose to evaluate the efficacy of sorafenib in children with LGAs in a translational clinical trial, stratified by BRAF status and tumor grade. The investigators expect to learn the following from this clinical translational trial: * The anti-tumor activity of sorafenib in pediatric LGAs * The safety and tolerability of sorafenib in pediatric patients with LGAs * The association of molecular target expression, e.g. oncogenic BRAF, with response rates The investigators will use the results of the clinical translational trial to determine if sorafenib warrants further clinical study in pediatric LGAs. If the investigators find associations between molecular target expression and response, further studies may be limited to or focus on patients whose tumors have specific molecular features, such as oncogenic BRAF. Sorafenib has also shown promise in combination with classic chemotherapy and can be given together with carboplatin, which is one of the most active agents in LGAs. Therefore, possible synergy between sorafenib and traditional chemotherapy used in the treatment of LGAs, such as carboplatin, could be explored in future clinical trials.