Low-grade astrocytoma

Low-grade astrocytoma (also known as WHO grade I or grade II astrocytoma) is a slow-growing tumor of the central nervous system that arises from astrocytes, the star-shaped glial cells that support neurons in the brain and spinal cord. This category includes pilocytic astrocytoma (grade I) and diffuse astrocytoma (grade II). These tumors most commonly occur in the brain but can also develop in the spinal cord, optic pathways, and brainstem. While they are considered less aggressive than high-grade astrocytomas, they can still cause significant morbidity depending on their location and size. Symptoms vary based on tumor location but commonly include headaches, seizures, focal neurological deficits (such as weakness or sensory changes), visual disturbances (particularly when the optic pathway is involved), balance and coordination problems, and personality or cognitive changes. In children, pilocytic astrocytomas frequently arise in the cerebellum and may present with signs of increased intracranial pressure such as nausea, vomiting, and papilledema. Some low-grade astrocytomas are associated with genetic predisposition syndromes, most notably neurofibromatosis type 1 (NF1), in which optic pathway gliomas are a hallmark feature. Molecular alterations commonly found include BRAF gene fusions or mutations (particularly in pilocytic astrocytomas) and IDH1/IDH2 mutations (in adult diffuse astrocytomas). Treatment depends on tumor type, location, and the patient's age and symptoms. Surgical resection is the primary treatment and may be curative, particularly for well-circumscribed pilocytic astrocytomas that can be completely removed. When complete resection is not feasible, observation with serial imaging (watch-and-wait strategy) may be appropriate, especially in asymptomatic or minimally symptomatic patients. Radiation therapy and chemotherapy are reserved for cases of tumor progression, recurrence, or when surgery is not possible. Targeted therapies, including MEK inhibitors and BRAF inhibitors, are emerging as promising treatment options, particularly for tumors harboring BRAF alterations. Overall prognosis is generally favorable compared to high-grade gliomas, with many patients surviving for years or decades, though the risk of malignant transformation exists, particularly for grade II diffuse astrocytomas.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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