Increasing CRC Screening in Community Health Centers through Mobile Messaging Optimization - Colorectal cancer (CRC) is the second leading cause of cancer death in the US, and differences among population groups are well-documented. A significant proportion of the difference in incidence and mortality between groups is directly attributable to screening rates. Community Health Centers (CHCs), which provide care for millions of patients across the US, have screening rates far below national averages. CHCs are struggling to re-engage patients, at least in part due to staffing shortages and the volume of screenings needed. Recent recommendations to start screening at age 45 has only added to the screening burden for CHCs. Text message reminders are a low cost, scalable way to deliver reminders, especially when integrated into population health management systems that can automatically deploy reminders. These reminders typically have small effect sizes, likely because few text message programs have been optimized to incorporate behavioral theories or communication strategies that can impact effectiveness. We will use our established partnership with the Mass League of Community Health Centers to optimize a mobile messaging intervention available for promotion of CRC screening by fecal immunochemical tests (FIT). With three CHCs from different regions of the US, we will use a two-phase process to first focus on reach, determining optimal messaging for maximizing patient engagement with a text campaign. We will then use a multi-level factorial randomized design to compare strategies for increasing screening completion. The text campaign will be offered with population management tools to track screening and abnormal follow-up completion. We will evaluate the sustainment of the intervention components over 12 months following completion of the intervention period. The proposed work uses a creative, community-engaged, systems-level approach to improve completion of FIT testing and abnormal follow-up among populations served by CHCs. Through the optimization of low burden strategies designed for community health centers, we can create an implementation ready solution to reach more CHC patients with this life- saving screening test. Results will likely be highly generalizable, as CHCs are increasingly turning to population management platforms to support their outreach systems, and thus optimizing their approach to implementing these tools will have widespread benefit.