BACKGROUND: More reliable clinical outcome prediction is required to better guide more personalized treatment for patients with primary glioblastoma multiforme (GBM). The objective of this study was to identify a microRNA expression signature to improve outcome prediction for patients with primary GBM. METHODS: A cohort of Chinese patients with primary GBM (n = 82) was analyzed using whole-genome microRNA expression profiling with patients divided into a training set and a testing set. Cox regression and risk-score analyses were used to develop a 5-microRNA signature using 41 training samples. The signature was validated in 41 other test samples, in an independent cohort of 35 patients with GBM, and in the Cancer Genome Atlas data set. RESULTS: Patients who had high risk scores according to the 5-microRNA signature had poor overall survival and progression-free survival compared with patients who had low risk scores. Multivariate Cox analysis indicated that the 5-microRNA signature was an independent prognostic biomarker after adjusting for other clinicopathologic and genetic factors, such as extent of resection, temozolomide chemotherapy, preoperative Karnofsky performance status score, isocitrate dehydrogenase 1 (IDH1) mutation, and O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status. CONCLUSIONS: The 5-microRNA signature was identified as an independent risk predictor that identified patients who had a high risk of unfavorable outcome, demonstrating its potential for personalizing cancer management. The authors concluded that this signature should be evaluated in further prospective studies. Cancer 2013. (c) 2012 American Cancer Society.