Abstract Background: Racial disparities in quality and completion of cancer treatment have been associated with poorer health outcomes among African Americans (AA) compared to White Americans (WA). Support from informal social networks – such as family members and friends - during the cancer care journey is critical. Yet, few studies have examined system-level factors associated with family and friend involvement in cancer care and whether system-level factors contribute to racial variations in their involvement. The purpose of this study is to investigate (a) cancer survivor perceptions on involvement of and effects from their informal social network during their cancer journey, (b) healthcare system factors that influenced the type and degree of network involvement, and (c) racial differences in survivor/network member experiences with the healthcare system during the cancer journey. Methods: Accountability for Cancer Care through Undoing Racism and Equity”, a 5-year system-change intervention trial funded by the National Cancer Institute, is a community-based participatory research (CBPR) partnership of the University of North Carolina at Chapel Hill (UNC), Greensboro Health Disparities Collaborative, and two cancer centers. ACCURE aims to reduce racial inequity in quality and completion of treatment for Stage 1-2 breast and lung cancer patients at the two partner cancer centers. As part of the formative work for this study, focus groups were conducted with Black and White early-stage breast and lung cancer survivors to understand how encounters with the healthcare system influenced their treatment experience (diagnosis through survivorship). Our racially diverse CBPR partnership developed, conducted, and analyzed focus group data from 8 focus groups with early stage breast and lung cancer survivors at the two cancer centers: 4 focus groups with AA survivors (n=12) and 4 focus groups with WA survivors (n=15). Results: Informal network member involvement was associated with barriers to care patients encountered in the cancer system; aspects of cancer care that helped to facilitate patient care and treatment; and, racial differences in critical encounters with the health system. Involvement with and health related experiences of family members and friends also influenced survivor interactions with the health care system, though differences by race were observed. Conclusion: Cancer survivors identified several healthcare system factors that influenced the nature of social network member involvement during cancer care, with some differences by race. Implications for system-changes to improve care for early-stage breast and lung cancer patients and survivors, and considerations of family and friend involvement in care, will be discussed. Citation Format: Katrina R. Ellis, Jennifer Schall, Stephanie Baker, Kristin Zenee Black, Carol Cothern, Kia Davis, Kay Doost, Eugenia Eng, Christina Goettsch, Fatima Guerrab, Christina Hardy, Alexandra Lightfoot, Neda Padilla, Cleo Samuel. A System-Change and Community-Based Participatory Research Approach to Understanding the Role of Informal Social Networks During the Cancer Care Journey. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr A43.