The potential of metformin as an antineoplastic in brain tumors: A systematic review

Brain tumors are challenging to handle and cause severe mortality and morbidity. The primary therapy for brain tumors, a combination of radiotherapy, chemotherapy (i.e temozolomide), and corticosteroids, is considered inadequate to improve patients' clinical conditions and associated with many adverse effects. There is an urgent need for new compounds or repurposing of existing therapies, which could improve brain tumor patients' prognosis. Metformin, commonly used for type 2 diabetes medication, has been examined for its protective action in cancer, reducing cancer risk and cancer-related mortality. However, its effect on cancer is still in rigorous debate. This study examines recent studies on the effects of metformin in primary brain tumor patients through systematic reviews. The literature search was performed on PubMed, ScienceDirect, and SpringerLink databases for articles published between 2013 and 2020. We selected clinical studies comparing the therapeutic outcomes of brain tumor therapy with and without metformin. The clinical benefits of the drug were assessed through the overall survival (OS) and progression-free survival (PFS) of brain tumor patients. Those studies demonstrated that the combination of metformin with temozolomide given post-radiotherapy resulted in better OS and PFS. Nonetheless, the efficacy and safety of metformin need further clinical testing in the wider population.