Inclusion Criteria:

• Patients must have histologically confirmed diagnosis of WHO grade IV primary malignant glioma (glioblastoma multiforme or gliosarcoma). Patients have to be able to undergo a GTR.
• Age > or = 18 years
• Evidence of a unilateral, single focus of measurable CNS neoplasm on contrast-enhanced MRI, unless medically contraindicated (CT scan will then be used)
• Patients must have < or = 2 disease progressions
• An interval of at least 4 weeks from the end of prior radiotherapy or one week from the end of a cycle of chemotherapy and enrollment on this protocol
• Karnofsky > or = 70%
• Hemoglobin > or = 9.0 g/dl, ANC > or = 1,500 cells/microliters, platelets > or = 125,000 cells/microliters
• Serum creatinine < or = 1.5 mg/dl, serum SGOT and bilirubin < or = 1.5 times upper limit of normal
• Patients on corticosteroids must have been on a stable dose for 1 week prior to entry, if clinically possible, and the dose should not be escalated over entry dose level
• If patient received chemotherapy or investigational agent as part of their prior therapy, the patient must recover from all toxicities (> or = Grade 1) prior to enrollment on this protocol
• Signed informed consent approved by the Institutional Review Board
• No evidence of CNS hemorrhage on the baseline MRI or CT scans
• If sexually active, patients will take contraceptive measures for the duration of treatment as stated in the informed consent

Exclusion Criteria:

• Pregnancy or breast feeding. Women of childbearing potential must have a negative serum pregnancy test within 72 hours prior to treatment administration
• Multifocal disease
• Prior treatment with Gliadel
• Prior treatment with CPT-11 or Avastin
• Prior stereotactic radiosurgery or brachytherapy
• Co-medication that may interfere with study results; e.g. immuno-suppressive agents other than corticosteroids
• Active infection requiring IV antibiotics
• Acute or chronic renal insufficiency (a GFR <30 mL/min/1.73m2) or acute renal insufficiency of any severity due to hepato-renal syndrome or in the peri-operative liver transplantation period
• Inability, in the opinion of the study investigator, to comply with study and/or follow-up procedures
• Current, recent (within 4 weeks of the first infusion of this study), or planned participation in an experimental drug study other than a Genentech-sponsored Avastin cancer study
• Life expectancy of less than 12 weeks
• Active malignancy, other than superficial basal cell and superficial squamous (skin) cell, or carcinoma in situ of the cervix within last five years
• Inadequately controlled hypertension (defined as systolic blood pressure >150 and/or diastolic blood pressure > 100 mmHg)
• Prior history of hypertensive crisis or hypertensive encephalopathy
• New York Heart Association (NYHA) Grade II or greater congestive heart failure
• History of myocardial infarction or unstable angina within 6 months prior to Day 1
• History of stroke or transient ischemic attack within 6 months prior to Day 1
• Significant vascular disease (e.g., aortic aneurysm, requiring surgical repair or recent peripheral arterial thrombosis) within 6 months prior to Day 1
• History of hemoptysis (> or = 1/2 teaspoon of bright red blood per episode) within 1 month prior to Day 1
• Evidence of bleeding diathesis or significant coagulopathy (in the absence of therapeutic anticoagulation)
• Major surgical procedure, open biopsy, or significant traumatic injury within 28 days prior to Day 1 or anticipation of need for major surgical procedure during the course of the study
• Core biopsy or other minor surgical procedure, excluding placement of a vascular access device, within 7 days prior to Day 1
• History of abdominal fistula, gastrointestinal perforation within 6 months prior to Day 1
• Serious, non-healing wound, active ulcer, or untreated bone fracture
• Proteinuria at screening as demonstrated by urinalysis (urine protein)
• Known hypersensitivity to any component of Avastin
• Pregnancy (positive pregnancy test) or lactation. Use of effective means of contraception (men and women) in subjects of child-bearing potential