Astrocytoma natural history

If left untreated, all of patients with low grade astrocytomas will have a rapid growth of the tumor similar to high grade astrocytoma and all of the patients with high grade astrocytoma will become symptomatic and deteriorate. Astrocytoma being a space occupying lesion may have following complications depending on the location of the tumor including increased intracranial pressure, cognitive dysfunction, emotional disturbances, behavioral complications, visual defects and muscle weakness. Low-grade astrocytomas (grade I [pilocytic] and grade II) have a relatively favorable prognosis, particularly for circumscribed, grade I lesions where complete excision may be possible. High-grade astrocytomas generally carry a poor prognosis in younger patients.

• Low grade astrocytoma:^[1][2][3][4]
  • The natural history of all low grade astrocytomas is not the same.
  • Most of the patients experience almost no progression of symptoms for initial 5 to 7 years.
  • If left untreated, all the patients with low grade astrocytomas will have rapid growth of tumor similar to high grade astrocytoma.
• High grade astrocytoma:
  • If left untreated, all of the patients become symptomatic and deteriorate.
  • Recurrence is more common in high grade astrocytoma compared to low grade astrocytoma.^[5]

• Astrocytoma being a space occupying lesion may have following complications depending on the location of the tumor:^[6][7][8]

• Increased intracranial pressure
• Cognitive dysfunction
• Emotional disturbances
• Behavioral complications
• Visual defects
• Muscle weakness
• Local neurological deficit

• Low-grade astrocytomas (grade I [pilocytic] and grade II) have a relatively favorable prognosis, particularly for circumscribed, grade I lesions where complete excision is possible.^{[9][10][11][12]}
• Tumor spread, when it occurs, is usually by contiguous extension; dissemination to other CNS sites may occur, although uncommon.^[13][14]
• Although, metastasis is uncommon, tumors may be of multi-focal origin, especially when associated with neurofibromatosis 1 (NF1).
• Unfavorable prognostic features for childhood low-grade astrocytomas include:^[15][16]

• Young age
• Fibrillary histology
• Inability to obtain a complete resection

• In patients with pilocytic astrocytoma, elevated MIB-1 labeling index, a marker of cellular activity, is associated with reduced progression-free survival.^[17][18]
• A BRAF-KIAA fusion, found in pilocytic tumors, confers a better clinical outcome.
• Children with isolated optic nerve tumors have a better prognosis than those with lesions that involve the chiasm or that extend along the optic pathway.^[19][20]
• Children with NF1 also have a better prognosis, especially when the tumor is found in asymptomatic patients at the time of screening.
• Grade 2 astrocytomas are defined as being invasive gliomas, meaning that the tumor cells penetrate into the surrounding normal brain.
• People with oligodendrogliomas (which might share common cells of origin) have better prognosis than those with mixed oligoastrocytomas, who in turn have better prognosis than patients with (pure) low-grade astrocytomas.
• Individuals with grade 2 astrocytoma have a 5-year survival rate of about 34% without treatment and about 70% with radiation therapy. The median survival time is 4 years.^[21]

• Biologic markers, such as p53 overexpression and mutation status, may be useful predictors of outcome in patients with high-grade gliomas.
  • MIB-1 labeling index is predictive of outcome in childhood malignant brain tumors.^[22]
  • Both histologic classification and proliferative activity evaluation have been shown to be independently associated with survival.^[23]
• Although, high-grade astrocytomas generally carry a poor prognosis in younger patients, those with anaplastic astrocytomas in whom a gross-total resection is possible may fare better.
• For low grade astrocytomas, removal of the tumor will generally allow functional survival for many years.
• In some reports, the five-year survival has been over 90% with well resected tumors.
• To date, complete resection of high grade astrocytomas is impossible because of the diffuse infiltration of tumor cells.
• Radiation therapy has been shown to prolong survival and is a standard component of treatment of anaplastic astrocytoma.
• Individuals with grade 3 astrocytoma have a median survival time of 18 months without treatment (radiation and chemotherapy).
• Although radiotherapy rarely cures glioblastoma multiforme, studies show that it doubles the median survival of patients, compared to supportive care alone.
• The prognosis is worst for these grade 4 gliomas.^[24][25][26]
  • Few patients survive beyond 3 years.
  • Individuals with grade 4 astrocytoma have a median survival time of:
    • 17 weeks without treatment,
    • 30 weeks with radiation
    • 37 weeks with surgical removal of most of the tumors.

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