Preservation of cognitive function following whole brain radiotherapy in patients with brain metastases: Complications, treatments, and the emerging role of memantine.

Whole brain radiotherapy is the mainstay of treatment for patients suffering from stage IV malignancies that have metastasized to the brain. Although this therapy is often effective at reducing tumor size and burden, it is associated with a spectrum of toxicities that often result in irreversible cognitive decline. Various drug and non-drug therapies have been evaluated to treat this neurotoxicity after whole brain radiotherapy is administered; however, currently available options have shown little benefit or come with side effects themselves that may outweigh the benefits of their use. For this reason, current investigations are focusing on preventing cognitive decline, rather than attempting to attenuate symptoms after they occur. Memantine has consistently shown promise in both in-vitro and in-vivo studies as a neuroprotective agent that may improve cognitive outcomes in patients undergoing whole brain radiotherapy. Memantine use prior to and during whole brain radiotherapy has been shown to significantly delay time to cognitive failure and reduce the rate of decline in memory, cognitive function, and processing speed. Its use has also been linked to significant decreases in brain edema, brain infarct size, and brain vasculature changes following whole brain radiotherapy. Memantine offers a promising safety profile with high tolerability and limited side effects. The objective of this article is to provide an overview of the target patient population, the neurotoxic effects of WBRT, current treatment options, and a summary of the available literature surrounding the use of memantine in this setting.