Complementary and Alternative Medicine for the Treatment of Gliomas: Scoping Review of Clinical Studies, Patient Outcomes, and Toxicity Profiles

Introduction: Complementary and alternative medicine (CAM) are highly used among those diagnosed with glioma. Further research is warranted, however, as it remains important to clearly delineate CAM practices that are unproven, disproven, or promising for future research and implementation. Methods: A systematic review was conducted to identify all articles that investigated the effect of any CAM therapy on survival of patients with newly diagnosed or recurrent glioma. Results: Eighteen papers and 4 abstracts pertaining to the effects of ketogenic diet (4), antioxidants (3), hyperbaric oxygen (4), cannabinoids (2), carbogen and nicotinamide (3), mistletoe extract (2), hypocupremia and penicillamine (1), and overall CAM use (3) on overall and progression-free survival in patients with low- and high-grade glioma were identified (Levels of Evidence I-IV). Ketogenic diets, hyperbaric oxygen therapy, and cannabinoids appear to be safe and well tolerated by patients; preliminary studies demonstrate tumor response and increased progression-free survival and overall survival when combined with standard of care therapies. Antioxidant usage exhibit mixed results perhaps associated with glioma grade with greater effect on low-grade gliomas; vitamin D intake was associated with prolonged survival. Conversely, carbogen breathing and hypocupremia were found to have no effect on the survival of patients with glioma, with associated significant toxicity. Most modalities under the CAM umbrella have not been appropriately studied and require further investigation. Conclusions: Despite widespread use, Level I or II evidence for CAM for the treatment of glioma is lacking, representing future research directions to optimally counsel and treat glioma patients.