Efficacy and safety of immunotherapies for the treatment of high-grade gliomas: a systematic review and meta-analysis

Background/Aim: High-grade gliomas are aggressive brain neoplasms usually refractory to treatment. Recently new treatment approaches have emerged, including immunotherapies. Hence, the aim of the present study was to evaluate the efficacy and safety of immunotherapies in adult patients with high-grade gliomas. Methods: Searches were performed in three databases for relevant studies published until December 2020. Title and abstract screening, full-text review, data extraction, and risk of bias assessment were performed independently by two reviewers. Risk of bias assessment was performed according to the revised Cochrane risk-of-bias tool for randomized trials (RoB 2). Meta-analyses were performed with Review Manager software (version 5.4.1), using risk ratio and 95% confidence intervals as measure of effect, the Mantel-Haenszel method, and random effects models. The quality of evidence assessment was conducted according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Results: Nineteen studies were included in the systematic review, of which 15 reported comparable data for meta-analyses. The outcomes assessed in the meta-analyses were overall survival (OS) and progression-free survival (PFS), with subgroups at 6, 12, and more than 12 months. No statistical differences were observed between immunotherapy and conventional treatment, except for the OS subgroup over 12 months. The certainty on the evidence was moderate. Conclusion: There was no evidence of an additional benefit of immunotherapy compared to standard treatment in the synthesis of results from clinical trials. Further high-quality clinical trials are needed to improve the quality of evidence concerning immunotherapies for the treatment of high-grade gliomas.