The purpose of this study is to show if prolonging treatment with temozolomide to 12 cycles improve progression-free survival in patients with glioblastoma included in this study, randomized according to o6-methylguanine-DNA-methyltransferase (MGMT) methylation status and residual disease or not, to receive an additional 6 cycles of temozolomide.

Inclusion Criteria:

1. Ability to understand and sign the informed consent document .
2. Age greater than or equal 18.
3. Patients with glioblastoma according to WHO classification (glioblastoma ) who received chemo- radiotherapy and temozolomide -based chemotherapy ( Stupp scheme ) and have completed 6 cycles of adjuvant temozolomide (with or without bevacizumab) in the context of standard treatment without presenting progression of disease.
4. Availability of tumor tissue from the first surgery for centralized histological review , for determining the MGMT study if you have not done in the center of origin. (If they were made in the center of origin the result of the center will be accepted ).
5. Stable dose of dexamethasone in the inclusion never above corticoids dose received in cycle 6 of the adjuvant .
6. Index greater than or equal 60 % Karnofsky.
7. All patients must show no progression of disease in a brain nuclear magnetic resonance (NMR) as defined in RANO established criteria before randomization .
8. Basal NMR study on a maximum of 6 weeks prior to inclusion, in which no progress is observed and is permitted to manage the care 6th cycle ( NMR performed after the 6th cycle of adjuvant is also acceptable as long as no progression was observed).
9. Adequate bone marrow reserve : hematocrit greater or equal 29% , white blood cell> 3,000 , RAN greater or equal 1,500 cells / ul , platelets greater or equal 100,000 cells / ul.
10. Creatinine <1.5 times the upper limit of normal (ULN) of the laboratory performing the analysis.
11. Serum bilirubin <1.5 / ULN; SGOT , SGPT < 2.5 times the upper limit of normal of the laboratory performing the analysis. Serum < 3/ULN alkaline phosphatases .
12. Effective contraceptive method in patients and their partners.

Exclusion Criteria:

1. Less than 5 years of any previous invasive neoplasia. In situ cervical carcinoma or basal cell skin carcinoma accepted.
2. Concomitant treatment with other investigational agents (other concomitant bevacizumab) .
3. Presence of any clinically significant gastrointestinal abnormalities that may affect the decision , transit or absorption of study drug , such as the inability to take medication in tablets by mouth.
4. Presence of any psychiatric or cognitive disorder that limits understanding or written informed consent and / or impair compliance with the requirements of this protocol.
5. Concurrent disease that prevents the continuation of temozolomide treatment.
6. Presence of leptomeningeal dissemination.
7. Pregnant or breastfeeding.
8. Positive patients receiving combination antiretroviral therapy in HIV