Medulloblastoma/Primitive neuroectodermal tumor and germ cell tumors: the uncommon but potentially curable primary brain tumors

Medulloblastoma: toward biologically based management

Medulloblastoma is the most common malignant brain tumor in children and, as such, has been the focus of tremendous efforts to genomically characterize it. What was once thought to be a single disease has been divided into multiple, molecularly unique subgroups through gene expression profiling. Each subgroup is not only unique in its origin and pathogenesis but also in the prognosis and potential therapeutic options. Targeted therapy of malignancies has long been the goal of clinical oncology. The progress made in the classification of medulloblastoma should be used as a model for future studies. With the evolution of epigenetic and genomic sequencing, especially when used in tandem with high-throughput pharmacologic screening protocols, the potential for subgroup-specific targeting is closer than ever. This review focuses on the development of the molecular classification system and its potential use in developing prognostic models as well as for the advancement of targeted therapeutic interventions.

Targeted treatment for sonic hedgehog-dependent medulloblastoma

Novel treatment options, including targeted therapies, are needed for patients with medulloblastoma (MB), especially for those with high-risk or recurrent/relapsed disease. Four major molecular subgroups of MB have been identified, one of which is characterized by activation of the sonic hedgehog (SHH) pathway. Preclinical data suggest that inhibitors of the hedgehog (Hh) pathway could become valuable treatment options for patients with this subgroup of MB. Indeed, agents targeting the positive regulator of the pathway, smoothened (SMO), have demonstrated efficacy in a subset of patients with SHH MB. However, because of resistance and the presence of mutations downstream of SMO, not all patients with SHH MB respond to SMO inhibitors. The development of agents that target these resistance mechanisms and the potential for their combination with traditional chemotherapy and SHH inhibitors will be discussed. Due to its extensive molecular heterogeneity, the future of MB treatment is in personalized therapy, which may lead to improved efficacy and reduced toxicity. This will include the development of clinically available tests that can efficiently discern the SHH subgroup. The preliminary use of these tests in clinical trials is also discussed herein.