PROJECT SUMMARY / ABSTRACT Roughly 90,000 adolescents and young adults (AYAs: 15–39) are diagnosed with cancer in the United States each year. Disparities in cancer mortality exist among AYAs with Ewing sarcoma (EWS) and osteosarcoma (OS), which may be partially due to unequal access to evidenced-based, standardized care (guideline concordant care; GCC). Many AYAs with cancer do not receive GCC, especially those with who are older and with limited resources. My prior research demonstrated 50% of AYAs with OS in California received guideline concordant care and the absence of such care negatively impacted survival. Increasing delivery of guideline concordant care in this patient population could markedly improve survival, especially in traditionally underserved patients (e.g., those with public insurance, other than White race/ethnicity). The barriers to the delivery of guideline concordant care are not clearly identified in AYAs. To fill this critical gap and gain essential training, I will employ an implementation mapping process to develop strategies that increase adoption of evidence-based practices, identify barriers and facilitators to the delivery of guideline concordant care, and develop an implementation blueprint to pilot an intervention to improve delivery of GCC in AYAs with EWS and OS. The specific aims are: 1) Identify barriers and facilitators to delivery of GCC for AYA patients with EWS and OS, 2) Systematically develop a tailored implementation blueprint for delivery of GCC care for AYA patients with EWS and OS, and 3) Evaluate the feasibility and acceptability of a cancer care delivery implementation blueprint to improve delivery of GCC in a pilot trial. The long-term goal of my research program is to improve cancer health equity for AYA patients with cancer. The proposed research and training plan supports my need to: (1) Expand skills in qualitative methods (i.e., thematic analysis); (2) Develop skills in implementation science methods; (3) Gain e