PROJECT SUMMARY/ABSTRACT Facilitating the successful transition of survivor care from pediatric to adult settings is critical to the long-term health of childhood cancer survivors (CCS) since their morbidity and mortality risks increase significantly over time. Yet, studies have shown that the majority of adult CCS no longer engage in survivor care after leaving the pediatric setting leading to disparities in survivorship outcomes. The Six Core Elements of Health Care Transition (HCT) from the U.S. Center for HCT Improvement aid in transition readiness for patients aging out of pediatric healthcare. Our survey of Children’s Oncology Group (COG) institutions found that nearly 2/3 of pediatric programs transition young adult (YA) CCS; however, less than half have an established transition process and none incorporated all six recommended HCT elements. Based on pilot data, approximately 50- 65% of local CCS who age out of pediatric care transfer survivor care to the dedicated adult CCS program, while the remainder seek care outside the Winship Cancer Institute or report no survivor care post-discharge. While many studies have evaluated patient- and provider-level barriers and facilitators to successful transition in YA CCS, there is a paucity of data characterizing organizational influences on HCT. The objectives of the current study are to describe: 1) what are the most salient organizational activities that could improve transition outcomes for YA CCS and 2) how to mitigate organizational barriers and leverage facilitators to improve HCT care delivery for CCS. Specifically we aim to: Evaluate organizational programming needed to promote continuation of risk-based survivor care among YA CCS (Aim 1), and Identify organizational barriers and facilitators to implementing the Six Core Elements of Transition in the context of survivor care (Aim 2). To accomplish these aims, we will conduct a mixed-method study of YA CCS, their parents, and pediatric and adult survivor healthcare providers. First, N~360 YA CCS who aged out of local pediatric care between 2016- 2020 will be re-contacted to determine patterns of successful HCT (i.e., initial survivor-focused adult healthcare visit ≤18 months post-discharge). CCS and their parents will be sent a HCT Feedback Survey to evaluate their perceptions of organizational barriers and facilitators affecting CCS transition and programming that could improve HCT. Additionally, pediatric and adult survivor care providers (n=15 from the Winship catchment area, n=15 from other COG institutions) will complete a HCT Feedback Survey and qualitative interviews focused on current transition processes as well as barriers and facilitators to implementing the Six Core Elements of HCT at their institution. The findings from this supplement will be used to inform organizational changes to improve HCT support for CCS at the Winship Cancer Institute and to develop a HCT toolkit to help other cancer centers address organizational barr...