Optic Pathway Gliomas

Although comprising only 1% of all brain tumors, optic pathway glioma (OPG) is the most common optic pathway tumor. While many cases are found in young children, 20–40% are found in patients ≥15 years. Neurofibromatosis type 1 (NF1) is a well-known risk factor, with about 15–20% of NF1 developing OPG which tends to be more indolent than the non-NF1 OPG. Most are pilocytic astrocytomas, but other types of low-grade and malignant gliomas have been reported. The role of surgery is to obtain tissue diagnosis or resection in the patient with a glioma confined just to the optic nerve and complete visual loss. Chemotherapy consisting of carboplatin and vincristine is a popular treatment approach to delay radiotherapy (RT) in children <10 years and preserve neurocognitive function. Targeted therapies such as bevacizumab and selumetinib are additional therapeutic options under investigation. In NF1 patients, RT is often avoided because of the higher chance of developing vascular and neoplastic events. RT is the mainstay of treatment for non-NF1 patients who are ≥10 years. The 10-year overall survival and progression-free survival rates range from 80% to 95% and 70% to 85%, respectively, with RT. In addition, stabilization and improvement in vision have been observed in more than 70% of patients receiving RT.