Low-Grade Gliomas

Abstract

Low-grade gliomas (LGG) are uncommon central nervous system (CNS) tumors which often present with seizures and few other neurologic signs or symptoms. Multimodality therapy encompassing surgical resection, radiation therapy (RT), and chemotherapy may provide the best disease-free and overall survival (OS). Each of these treatment modalities plays an important role in the treatment of these tumors. The understanding and management of LGG is evolving as randomized clinical trials have begun to address many questions related to the timing and order of each of the available treatments and their individual and combined effects on progression-free survival (PFS) and OS. Currently, an attempt at surgical resection followed by external beam RT is a typical treatment approach, at least in high-risk patients. Observation with serial brain imaging studies or surgical resection or debulking alone may be acceptable options in patients with low-risk tumors. The role of chemotherapy in either group is less clear, but recent studies have indicated that concurrent chemotherapy with radiation improves PFS and may eventually impact OS. The European Organization for Research and Treatment of Cancer (EORTC) and the Radiation Therapy Oncology Group (RTOG) are currently conducting two large Phase III and Phase II studies, respectively. The studies seek to evaluate the efficacy of radiotherapy and either temozolomide or a combination of procarbazine, vincristine, and lomustine in high-risk LGG patients. Ongoing investigative efforts seek to confirm the predictive value of a number of molecular markers including the loss of chromosomes 1p and 19q and the epigenetic silencing of the methylguanine-DNA methyltransferase (MGMT) gene. Additional smaller clinical trials seek to establish the role of newer targeted therapies including small-molecule tyrosine kinase inhibitors in patients with newly diagnosed and recurrent LGG.