Prevention of Thrombocytopenia in Glioblastoma Patients

Inclusion Criteria: * Histological proof of newly diagnosed glioblastoma, * Age: 18 and older, * Information to patient and signed consent form, * Indication for a " Stupp " protocol (cerebral focal radiotherapy and concomitant TMZ followed by adjuvant TMZ - 6 cycles), * Patient with grade 3 or 4 TP during Temozolomide chemotherapy, regardless of when the onset of TP was: after completion of concomitant RT/CT, before adjuvant CT or during adjuvant CT and only if a minimum of 2 cycles are still planned, * Normal initial platelets count (\> 100 000/mm3) before the start of Temozolomide during the RT/CT concomitant phase, * Adequate haematological, renal, hepatic function at the time of inclusion visit, * ECOG PS 0-2 (patients unable to walk because of a paralysis and who are up in a wheel chair will be considered as ambulatory for the evaluation of the ECOG performance status), * Life expectancy \> 2 months, * Patients covered by the French Health Insurance System, * Negative pregnancy test at the time of inclusion visit, * If required, effective contraception respecting criteria of CPMP/ICH/286/95 (such as implants, injectables, combined oral contraceptives, some IUDs, sexual abstinence or vasectomised partner). Exclusion Criteria: * Concomitant radiotherapy (Romiplostim will be started after the completion of the RT/CT concomitant phase), * Other malignancies (prior hx malignancies), * Any anterior systemic chemotherapy, * Any known coagulation disease or known haematological disease even if resolved. Known hypercoagulate state (e.g., factor V Leiden, protein C defiency, protein S deficiency, PT 20201, antiphospholipid antibody syndrome…), * Prior Romiplostim exposure or prior exposure to other TPO mimetics, * History of thromboembolic disease \< 6 months. Treatment with anticoagulant such as Heparin or antivitamin K (LMWH as prophylactic treatment is authorized), * Any other hemato-toxicity (anemia, neutropenia) requiring EPO or GCSF, * Other causes of Temozolomide interruption (non haematological toxicities), * Known hypersensitivity to any E-coli derived product, * Participation to any other study during the last 30 days, * Refusal to give written informed consent, * Pregnancy or nursing, * For all men and women of childbearing potential: Refusal or inability to use effective means of contraception, * Any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial, * Persons protected by a legal regime (guardianship, trusteeship), * Patients in emergency situations, * Patients kept in detention.