Inclusion Criteria:

- Progressive or recurrent glioblastoma documented by MRI no earlier than 180 days
after first surgery for glioblastoma and no earlier than 90 days after completion of
radiotherapy.

- Histological diagnosis of glioblastoma

- Tissue available for the determination of MGMT promoter methylation in the primary
tumor or from the recurrent tumor if a patient undergoes a surgical procedure at
recurrence prior to study entry.

- Prior treatment with temozolomide administered concomitantly with radiotherapy and at
least for two cycles (5/28) as an adjuvant treatment

- Informed consent

- Age 18-80 years

- Karnofsky performance score > 50%

- Neutrophil counts > 1 500/µl

- Platelet counts > 100 000/µl

- Hemoglobin > 10 g/dl

- Serum creatinin < 1.5-fold upper normal range

- ASAT or ALAT < 3-fold upper normal range unless attributed to anticonvulsants

- Alkaline phosphatase < 3-fold upper normal range

- Women with childbearing potential must have a negative serum pregnancy test ≤14 days
prior to study enrollment

- Willingness to apply contraception according to local requirements (as stated in
patient information)

Exclusion Criteria:

- Progressive or recurrent glioblastoma documented by MRI earlier than 180 days after
first surgery for glioblastoma and earlier than 90 days after completion of
radiotherapy.

- Treatment with any chemotherapy other than temozolomide according to the schedule of
the EORTC NCIC trial (Stupp et al. N Engl J Med 2005;352:987-996) except that an
adjuvant starting dose of 200 mg/m2 and more than 6 cycles of adjuvant temozolomide
are allowed

- Prior systemic or local treatment with DNA-damaging agents, tyrosine kinase
inhibitors or anti-angiogenic agents for any cancer

- Allergy to or other intolerability of temozolomide

- Unable to undergo MRI

- Past medical history of diseases with poor prognosis, e.g. severe coronary heart
disease, severe diabetes, immune deficiency, residual deficits after stroke, severe
mental retardation

- HIV infection

- Pregnancy

- Breast feeding

- Treatment within in any other clinical trial parallel to the treatment phase of the
current study