PROJECT SUMMARY/ABSTRACT Due to advances in detection and treatment, there is a rapidly increasing population of survivors of pediatric brain tumor. With increased survival rates, there is greater emphasis on managing the late effects of pediatric brain tumor. Cognitive symptoms are prevalent among survivors and are associated with poor academic achievement, vocational success, and overall quality of life. However, few interventions have been trialed to reduce cognitive symptoms. To this end, fatigue is a common late effect of brain tumor and its treatment, and it significantly reduces cognitive efficiency, including attention and speed of processing information. Among survivors, interventions that are low cost, non-pharmacological, and appropriate for self-management are highly desired but rare. Systematic bright light exposure has been shown to be effective for improving sleep and reducing fatigue among adolescent and adult patient populations, including adolescent and young adult solid tumor, and adult cancer survivors. The purpose of the proposed study is to evaluate the feasibility and preliminary effectiveness of systematic bright light exposure for reducing fatigue and improving cognitive efficiency among pediatric brain tumor survivors. Forty survivors (ages 10-18 years) will be asked to wear systematic light exposure glasses for 30 minutes upon awakening for a six week period with follow-up at 2- weeks post-intervention. Systematic bright light exposure (intervention) will be compared to dim light exposure (placebo-control). As part of this study, we focus on intervention fidelity, using an integrated app recording timing and duration of light exposure; and adverse side effects associated with light exposure. We assess preliminary outcomes associated with patient and parent-proxy reports of fatigue and cognitive efficiency using in-person and remote administration of a computerized battery. The ultimate goal of this line of research is to trial interventions that mitigate cognitive late effects to improve quality of life in pediatric brain tumor survivors. Findings from this pilot study will be used to refine the intervention and inform a larger randomized controlled trial.