Inclusion Criteria:

• Pts w gr II LGG that is recurrent/progressive following prior surgical resection while on non-decreasing dose of corticosteroids
• >25percent enlargement of bidimensional measure/new lesions on sequential imaging new &/or worsening neurologic deficits
• Pts w progressive/recurrent optic pathway tumors
• Pts have measurable disease on MRI/CT
• Interval of >4 wks between prior XRT/chemo,& enrollment on protocol unless there is unequivocal evidence of tumor progression & pt has recovered from all expected toxicities associated w prior therapy. Pts treated w chemo agents such as VP-16 who would normally be retreated after shorter intervals may be treated at usual starting time even if <4 wks from last prior dose of chemo
• Pts not have had tumor biopsy <1 wk/surgical resection <2 wks prior to starting study drug
• Pts enrolling on arm B must be on >1 enzyme inducing anticonvulsants for >2 wks prior to starting study drug
• Pts should be on non-increasing dose of steroids for >7 days prior to obtaining baseline Gd-MRI of brain
• Pts should be on non-increasing dose of steroids for >7 days prior to starting study drug
• Multifocal disease is eligible
• Age >18 yrs
• KPS of >60
• ANC >1.5 x 10 9/L
• Hgb >9 g/dL
• Platelets >100 x 10 9/L
• K ≥LLN/correctable w supplements
• Ca ≥LLN/correctable w supplements
• P ≥LLN/correctable w supplements
• AST/SGOT & ALT/SGPT <2.5 x ULN
• Serum bilirubin <1.5 x ULN
• Serum creatinine <1.5 x ULN/measured 24hr CrCl >50 mL/min/1.73m2
• Life expectancy ≥12wks
• Written informed consent obtained prior to screening procedures

Exclusion Criteria:

• Prior progressive disease/toxicity gr ≥3 w prior hydroxyurea therapy
• Prior treatment w imatinib/other PDGF-directed therapy
• Excessive risk of bleeding as defined by stroke <6 mths, history of CNS/intraocular bleed, or septic endocarditis
• Evidence of intratumor hemorrhage on pretreatment diagnostic imaging, except for stable post-operative gr1 hemorrhage
• Pregnant/breast feeding, /adults of reproductive potential not employing effective method of birth control
• Concurrent severe and/or uncontrolled medical disease that could compromise participation in study
• Acute/chronic liver disease
• Confirmed diagnosis of HIV infection
• Impairment of GI function/GI disease that may significantly alter absorption of imatinib
• Pts taking Coumadin
• Pts have received investigational drugs <2wks prior to entry on study/have not recovered from toxic effects of such therapy
• Pts have received biologic, immunotherapeutic/cytostatic agents <1 wk prior to entry on study/have not recovered from toxic effects of such therapy
• Pt >5 yrs free of another primary malignancy except: if other primary malignancy is not currently clinically significant/requiring active intervention, or if other primary malignancy is basal cell skin cancer/ cervical carcinoma in situ. Existence of any other malignant disease is not allowed
• Pts have had any surgery other than resection of brain tumor <2 wks prior to entry on study/have not recovered from side effects of such therapy
• Pts unwilling to/unable to comply w protocol
• Active systemic bleeding, such as GI bleeding/gross hematuria
• Gr2 /> peripheral edema/central/systemic fluid collections
• Pts who enroll on arm A must have not received any EIAC for >2 wks prior to starting study regimen
• Any of following exclusion criteria to MRI imaging:Cardiac pacemaker, Ferromagnetic metal implants other than those approved as safe for use in MR scanners, Claustrophobia, Obesity