Patients with glioblastoma face a grim prognosis. Despite recent advancement in neurosurgical technology and neuro-oncology glioblastomas almost invariably progress or recur after a median of 4-8 months. The strategy to repeat tumor resection at recurrence in order to minimize tumor load and thus to facilitate subsequent second-line therapy has been shown to be feasible and safe. However, evidence for a survival benefit of surgery for recurrent glioblastoma is scarce and relies entirely on retrospective analyses. While most retrospective analyses report an apparent survival benefit, an EORTC meta-analysis on second-line therapies found no survival difference in patients with or without surgery at recurrence. With regard to the risks and costs inherent to surgery for glioblastoma, a randomized controlled trial is required. The purpose of the study is to compare the effect of craniotomy and tumor resection followed by adjuvant second-line therapy to no surgery followed by second-line therapy on overall survival, neurological status, and quality of life. Analysis of overall survival will be used to improve sample size estimation of a subsequent phase III trial for craniotomy and tumor resection of glioblastoma recurrence in cooperation with the EORTC.