PROJECT SUMMARY Lung cancer is the leading cause of cancer death in the US, with most lung cancer diagnosed at advanced stages. Low-dose CT screening of high-risk individuals is the only evidence-based tool available to diagnose lung cancer at an early stage when curable treatment options exist. The promising mortality reduction benefit of lung cancer screening (LCS) is presently overwhelmingly unfulfilled due to suboptimal population-based adherence to annual screening guidelines. Outside of research settings, adherence to annual LCS is less than half of the rates observed in the practice-changing, landmark clinical trials. There is an urgent need for effective and feasible interventions to improve LCS adherence and achieve optimal individual and population health benefits. Research during the F99 phase will leverage an innovative, multi-phase, mixed methods design to describe how LCS patients process health information regarding health protective behavior and utilize this information to develop and evaluate reminder messages with individuals eligible for LCS. Using a four-step process, data collected in a survey of LCS program participants (step 1) will inform the development of a pool of candidate reminder messages (step 2). In the final two steps, the reminder messages will be evaluated by LCS experts (step 3) and further evaluated and refined with LCS program participants (step 4) using mixed methods, including surveys and interviews. Differences between health information processing constructs by demographic or clinical characteristics found to be significant from step 1 will be the focus for message targeting (group level) and/or tailoring (individual level). At the conclusion of the F99 phase, I will have a formalized set of clear, engaging, and efficient messages to support LCS annual adherence, ready to be evaluated in a clinical setting. Research proposed in the K00 phase will focus on gaining real-world experience with hybrid effectiveness implementation study designs and pragmatic outcome measures to simultaneously assess effectiveness and implementation outcomes. Specifically, I propose a mentored pre-post type 1 hybrid effectiveness- implementation trial, within a parent trial, that will allow concurrent assessment of effectiveness and implementation outcomes of the F99 reminder strategy in real-world LCS programs. Effectiveness will be tested using a pre-post design, comparing percent screening participants adherent to annual screening guidelines before and after implementation of the reminder strategy. Secondary implementation outcomes (i.e., acceptability and feasibility) will be assessed with surveys and key informant interviews of personnel involved in the reminder system implementation (e.g., LCS program directors, navigators, coordinators). This body of research will prepare me for a career as an independent cancer-focused intervention scientist with expertise in the development and implementation of effective, low-burden in...