1 ABSTRACT – OVERALL COMPONENT 2 3 The development of brain metastases, experienced by up to 40% of cancer patients, marks a clear inflection 4 point in survival and quality of life. The inaccessibility of brain tumor tissue has stymied progress in our 5 understanding and treatment of brain metastases, and patients are regularly excluded from clinical trials. The 6 Stanford Brain Metastasis Consortium has unified brain and cancer experts in the singular goal of improving our 7 understanding and treatment of brain metastases, a currently increasing yet underserved subset of cancer 8 patients. To accomplish the above goal, we have: (1) designed an organizational structure that supports 9 scientists in our integrated work; (2) developed highly innovative and complementary Projects to understand 10 and disrupt the cancer-neuro-immune axis supporting brain metastases; and (3) created NeuroPathology 11 and ToolKit Cores to make human specimens and cutting-edge technologies readily accessible to participating 12 scientists. We expect to identify and target key mediators of brain metastasis, with therapeutic benefit for 13 patients. 14 Little is known about the distinct mechanisms that drive tumor cells to the brain and allow them to grow in this 15 unique microenvironment, supported in part by normal brain cells. Streamlined access to human brain 16 specimens, combined with innovations in modeling and manipulation of the tumor microenvironment, create this 17 collaborative opportunity for fundamental advancement. Our expert, integrated team of productive collaborators 18 aims to understand how the intrinsic features of tumor cells (Project 1), resident microglia (Project 2), and the 19 systemic immune system (Project 3) contribute to the onset and progression of brain metastases. These projects 20 are facilitated by centralized access to human patient brain metastases samples (NeuroPathology Core), and 21 novel, multiplexed analyses and disease modeling (ToolKit Core). Our multidisciplinary physician Consultant 22 Network provides clinical insight and helps in the rapid translation of our findings into clinical trials for patients 23 with brain metastases. The Administrative and Data Management Core will provide the operational support 24 necessary to successfully achieve the goals of the program. Our Patient Advocates help to integrate and 25 communicate our work to the greater scientific and patient communities. 26 We have formed one of the few groups with the expertise, interest, and capacity to address the underlying 27 mechanisms of and therapeutic opportunities for brain metastases. Only through this combined synergy would 28 this project be possible. These innovative methods will ensure our findings are reflective of and translatable to 29 the human disease, enabling our multidisciplinary team to lay the foundation for diagnostic and therapeutic 30 advancements.