Molecular Advances of Brain Tumors in Radiation Oncology

Glioblastoma, grade IV malignant glioma based on the World Health Organization classification, is the most common primary brain tumor in adults. The average survival time of less than 1 year has not improved notably over the last 3 decades. Surgery and radiotherapy, the traditional cornerstones of therapy, provide palliative benefit, whereas the value of chemotherapy has been marginal and controversial. The dismal prognosis of glioblastoma patients is largely caused by the striking radioresistance of these tumors. A better understanding of the molecular mechanisms that underlie the malignant phenotype of glioblastomas and plausible mechanisms of radiation resistance can provide new possibilities in terms of targeted therapeutic strategies. Despite the genetic heterogeneity of malignant gliomas, common aberrations in the signaling elements of the growth and survival pathways are found. New treatments have emerged to target molecules in these signaling pathways with the goal to increase specific efficacy and minimize toxicity. Monoclonal antibodies and low molecular-weight kinase inhibitors are the most common classes of agents in targeted cancer treatment. This review introduces these new targeted therapies in the context of current treatment options for patients with glioblastoma. It is hoped that this combined approach will overcome the current limitations in the treatment of patients with glioblastoma and result in a better prognosis for these patients.