The Brain Tumor Epidemiology Consortium (BTEC) is an international consortium that fosters interdisciplinary collaborations focusing on research related to the etiology, outcomes, and prevention of brain tumors. The 21st annual BTEC meeting with the theme "Brain Tumor Biomarkers for Research, Clinics, and Registries" was held virtually from June 22 to 24, 2021. Scientists from North America and Europe, representing a broad range of brain tumor research interests, presented recent research and progress in the field. The meeting content is summarized in the following report.