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Pilocytic astrocytomas
Miriam Bornhorst1, Didier Frappaz2, Roger J Packer1
1Gilbert Family Neurofibromatosis Institute and Brain Tumor Institute, Children's National Health System, Washington, DC, USA.
Insights
Pilocytic astrocytoma (PA) is a common pediatric brain tumor. Discoveries reveal key genetic alterations in the Ras/ERK pathway, guiding promising new targeted therapies for better outcomes.
Area of Science:
- Pediatric neuro-oncology
- Molecular genetics of brain tumors
Background:
- Pilocytic astrocytoma (PA) is the most frequent pediatric brain tumor, characterized by slow growth and potential for spontaneous regression.
- PAs typically occur in the cerebellum and chiasmatic/hypothalamic regions but can arise elsewhere in the central nervous system, with rare dissemination.
- Neurofibromatosis type 1 predisposes children to PAs, particularly in the optic pathway.
Purpose of the Study:
- To review the key molecular alterations in pilocytic astrocytoma.
- To discuss current and emerging therapeutic strategies for pediatric PAs.
- To highlight prognostic factors influencing patient survival.
Main Methods:
- Review of existing literature on pilocytic astrocytoma.
- Analysis of genetic alterations, focusing on the Ras/ERK pathway.
- Examination of treatment modalities and survival data.
Main Results:
- KIAA1549-BRAF fusions are the most frequent genetic alteration identified in the Ras/ERK pathway in PAs.
- Complete surgical resection is associated with the best survival outcomes.
- Pediatric 10-year survival rates exceed 90%, though adult outcomes are poorer.
Conclusions:
- Targeted therapies directed at the Ras/ERK pathway represent a promising avenue for future treatment of PAs.
- Understanding molecular drivers is crucial for developing effective therapeutic strategies.
- Early diagnosis and complete resection significantly improve prognosis for pediatric pilocytic astrocytoma.
Abstract:
Pilocytic astrocytoma (PA) is the most common pediatric brain tumor in children. PAs are a distinct histologic and biologic subset of glioma that have a slow growth rate and may even spontaneously regress. These tumors tend to arise in the cerebellum and chiasmatic/hypothalamic region, but can also occur in other regions of the central nervous system. Dissemination is uncommon, but may occur in newly diagnosed PAs. Alterations in the Ras/RAF/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway (Ras/ERK) have been discovered in a majority of PAs, with KIAA1549-BRAF fusions being the most commonly identified alteration. Children with neurofibromatosis 1 are predisposed to developing PAs, primarily within the optic pathway. When required, treatment consists of surgery, chemotherapy, and/or radiation, although new molecular agents targeting the Ras/ERK and related signaling pathways are promising new approaches. The 10-year survival rates are greater than 90% in pediatric patients; however, they are poorer in adults. Tumors that are amenable to complete resection (i.e., cerebellum and cortex) have the best overall survival.
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