Objective: To evaluate the effectiveness of a personalized motivational messaging intervention designed to improve cognitive function in lung cancer survivors.

Hypothesis: Lung cancer survivors who receive personalized motivational messaging will demonstrate significantly greater improvements in cognitive function compared to those receiving standard care.

Design and Participants: A randomized controlled trial (RCT) comprising 196 lung cancer survivors experiencing cancer-related cognitive impairment.

Intervention: Participants in the intervention arm will be provided with a wearable activity tracker for three months and will receive personalized motivational messages via instant messaging applications (e.g., WhatsApp) to promote physical activity. The intervention comprises: (1) regular messages delivered at participant-preferred times and frequencies, enabling individuals to select from suggested physical activity goals; and (2) interactive, chat-based support facilitating goal setting, real-time counseling, and practical advice. The control group will receive an informational leaflet on cognitive impairment, along with text message reminders for follow-up assessments.

Main Outcome Measures: Data collection will occur at baseline (T0), three months (T1; immediately post-intervention), and six months (T2; long-term follow-up). The primary outcome is cognitive function, assessed objectively via the Hong Kong version of the Montreal Cognitive Assessment (HK-MoCA) and subjectively via the Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog) scale. Secondary outcomes include physical activity levels (IPAQ-SF), exercise self-efficacy (SEE), psychological well-being (PHQ-4), and health-related quality of life (EORTC QLQ-C30).

Data Analysis: Quantitative data will be analyzed using an intention-to-treat approach. Additionally, post-trial qualitative evaluations (to assess intervention compliance) and cost-effectiveness analyses will be performed. The study will strictly adhere to the CONSORT-EHEALTH reporting guidelines.

Expected Outcomes: This trial will provide robust evidence regarding the effectiveness of the proposed intervention in mitigating cognitive impairment and increasing physical activity levels among lung cancer survivors.

1. Background of the Research Project Lung cancer is a leading cause of cancer-related mortality worldwide. In Hong Kong, it accounts for over 26% of all cancer deaths, with 80% to 85% being non-small cell lung cancers (NSCLC). While cancer-related symptoms affecting overall survival and quality of life have been extensively studied, cancer-related cognitive impairment (CRCI) remains a critical yet under-researched complication. CRCI refers to cognitive dysfunction, including impaired working or short-term memory, inattention, disorientation, and declines in executive function, language comprehension, and processing speed. More than 50% of patients with non-central nervous system (CNS) cancers present with CRCI after primary treatments. Our preliminary pilot data indicated that the prevalence of cognitive impairment in attention and memory among lung cancer patients was 35.4% and 58.4%, respectively. CRCI significantly impacts patients' functional independence and can lead to anxiety, depression, and sleep disorders, highlighting an urgent need for effective, accessible interventions.

2. Theoretical and Clinical Background Clinically, several studies and systematic reviews have demonstrated that exercise and physical activity interventions can alleviate CRCI in cancer patients. However, traditional exercise programs often suffer from poor long-term adherence and a lack of sustained motivation once the formal intervention period ends. To address this translational gap, this study utilizes an Ecological Momentary Intervention (EMI) approach via mobile health (mHealth) technology. EMI delivers health interventions through instant messaging (IM) applications (e.g., WhatsApp) in a personalized, real-time, and in-situ format.

   Theoretically, the intervention is rigorously grounded in Social Cognitive Theory (SCT), which posits that personal and environmental factors influence health behaviors. The intervention design operationalizes key SCT constructs:

   Behavioral Capability: Providing tailored information to increase physical activity based on self-care needs.

   Outcome Expectations: Educating participants on how physical activity improves neurocognitive function.

   Observational Learning: Utilizing case vignettes of other survivors. Self-efficacy: Fostering belief in behavioral change through collaborative goal-setting and chat-based support.

   Reinforcement: Providing systematic feedback and positive validation on behavioral changes.

3. Objectives The primary objective of this randomized controlled trial (RCT) is to evaluate the effectiveness of an SCT-based, personalized motivational messaging intervention delivered via an instant messaging application in improving cognitive function among lung cancer survivors with CRCI. The secondary objectives are to assess the intervention's impact on physical activity levels, exercise self-efficacy, psychological well-being, and health-related quality of life, as well as to evaluate the cost-effectiveness and participants' qualitative experiences of the intervention.

4. Main Research Questions and Hypotheses Research Question: Does a personalized motivational messaging intervention, utilizing wearable activity trackers and real-time IM support, effectively mitigate cognitive decline and promote physical activity in lung cancer survivors compared to standard care?

   Hypotheses: We hypothesize that lung cancer survivors with CRCI receiving the personalized motivational messaging intervention will demonstrate (1) significantly greater improvements in objective and subjective cognitive function, and (2) significantly increased physical activity levels compared to those receiving standard care.

5. Study Design and Methods This study is a randomized controlled trial (RCT) comprising 124 lung cancer survivors, augmented by a post-trial qualitative process evaluation.

   Randomization and Blinding: Participants will be randomly allocated to either the intervention or control arm. A computer-generated randomization sequence will be created by an independent statistician using block randomization with varying block sizes (blocks of 4, 6, and 8). Allocation concealment will be maintained using sequentially numbered, opaque, sealed envelopes. Outcome assessors and the trial statistician will be blinded to group allocation.

   Intervention Arm: Participants will be equipped with a wearable activity tracker for 3 months. They will receive personalized motivational messages from a comprehensive message library developed by an oncology specialist and a research nurse trained in motivational interviewing. The intervention features two components: (a) regular message delivery whose frequency and timing are tailored to participant preferences, and (b) interactive chat-type support facilitating goal setting, real-time counseling, and practical advice.

   Control Arm: Participants will receive an informational leaflet containing basic CRCI education and standard text message reminders for follow-up assessments, without the personalized motivational or interactive chat components.

   Data Collection & Analysis: Quantitative assessments will occur at baseline (T0), 3 months (T1), and 6 months (T2). An Intention-to-Treat (ITT) analysis will be performed. Generalized Estimating Equations (GEE) will be utilized to estimate between-group and within-group differences across time points, adjusting for baseline covariates. GEE robustly handles missing longitudinal data without manual imputation.

   Economic & Qualitative Evaluation: A cost-effectiveness analysis will calculate the Incremental Cost-Effectiveness Ratio (ICER) using Quality-Adjusted Life Years (QALYs) derived from EORTC QLQ-C30 scores. Additionally, a post-trial qualitative study using purposive maximum variation sampling will conduct in-depth interviews (analyzed via 7-step thematic analysis in NVivo) to understand intervention compliance and participant experience.

6. Expected Outcomes The trial is expected to yield robust quantitative evidence that personalized EMI significantly improves cognitive domains (such as attention, verbal learning, and executive function) and sustains moderate-to-vigorous physical activity in lung cancer survivors. Furthermore, the trial is expected to demonstrate high feasibility, user acceptability, and cost-effectiveness compared to standard oncological supportive care.

7. Significance of the Study This study addresses a critical gap in cancer survivorship by targeting CRCI-a prevalent but frequently overlooked symptom. If proven effective, this intervention provides an efficient, highly scalable, real-world, and cost-effective digital health solution. Furthermore, the chat-log data and user preference profiles generated from this study will establish a foundational database for the future development of Artificial Intelligence (AI) chatbot services for physical activity management, aligning with global smart-city healthcare blueprints and advancing the implementation science of mHealth in oncology.

Inclusion Criteria:

1. aged ≥ 18 years;
2. diagnosed with stage I-III non-metastatic NSCLC cancer;
3. completed primary treatment with curative intent (surgery, chemotherapy and/or radiation therapy) 6 months to 5 years prior to the baseline assessment with no recurrence or occurrence of additional cancers;
4. identified as having mild cognitive impairment by the HK-MoCA 5-Min Protocol (≤ 7th age- and education-corrected percentile cut-off score);
5. not engaged in regular exercise (defined as < 150 min of moderate-intensity exercise per week).

Exclusion Criteria:

1. inadequate reading and verbal Cantonese comprehension for the study activities;
2. diagnosed with dementia;
3. unable to use mobile phone text messaging applications (e.g., WhatsApp).