astrocytoma prognosispilomyxoid astrocytoma prognosispilocytic astrocytoma prognosisanaplastic astrocytoma prognosisrecurrent astrocytoma prognosiscerebellar astrocytoma prognosispediatric astrocytoma prognosisglioma astrocytoma prognosisdiffuse astrocytoma prognosisfibrillary astrocytoma prognosisstage 3 astrocytoma prognosisspinal astrocytoma prognosis