The purpose of GLIOPLAK is to evaluate the predictive value of a biological test performed in the radio-chemotherapy phase in patients suffering from glioblastoma. The studied parameter is the variation in platelet count during the radio-chemotherapy phase. The main objective is to identify early in Stupp protocol a group of patients having high risk to undergo thrombocytopenia in maintenance phase of temozolomide. With this result an algorithm of platelet monitoring for patients treated with Stupp protocol wil be proposed.

Glioblastoma is the most common primitive cerebral tumor. Currently its optimal treatment is based on a multidisciplinary approach combining an initial surgical resection, if feasible, then Stupp protocol. Stupp protocol consists of two phases: first phase involves external radiotherapy with concomitant oral temozolomide at a dose of 75mg/m2 per day for about six weeks. After 4 weeks of therapy break, maintenance phase begins with temozolomide alone, for a period of 6 cycles (1 cycle = 5 days over 28). The dose of temozolomide is 150mg/m2 on the first cycle followed by 200 mg/m2. One major limiting toxicity of temozolomide is hematologic, especially thrombocytopenia. They occur in around 15 and 20% of patients in maintenance phase. Thrombocytopenia has an impact on the schedule of Stupp protocol such as dose reduction or even early discontinuation. Currently no predictive marker of thrombocytopenia in the maintenance phase was identified. Such marker could be of major interest to adapt biological and clinical follow-up by patient in maintenance phase. We conduct a retrospective analysis on a cohort of patients suffering from glioblastoma and treated with Stupp protocol. We found that a decrease in platelet count during the radio-chemotherapy phase could be highly predictive of protocol changes in maintenance phase of temozolomide due to thrombocytopenia. The main objective of GLIOPLAK is to prospectively confirm the predictive value of this test and to evaluate the prognostic impact of the occurrence of thrombocytopenia <100,000/mm3. Secondary objective of GLIOPLAK are to describe all limiting toxicities in maintenance phase, to constitute a prospective biological collection and to collect biological samples to perform pharmacological analysis (pharmacogenomics and pharmacokinetics parameters).

Inclusion Criteria:

• Age Superior to 18 years
• Inform consent form signed
• Newly diagnosed (histologically) glioblastoma
• Stupp protocol treatment
• with social insurance

Exclusion Criteria:

• Not inform consent form signed
• participation to another clinical trial
• other cancer
• background of hematological pathology
• patient under guardianship, curatorship