Survivors of childhood cancer have a substantially increased risk of long-term health problems in adulthood, including cardiovascular disease, metabolic disorders, psychological morbidity, and impaired health-related quality of life (HRQoL). These risks are partly related to cancer treatment exposures but are also strongly influenced by modifiable lifestyle factors such as physical activity, diet, body weight, and cardiometabolic risk factors. Although healthy lifestyle behaviors are known to reduce morbidity and mortality in this population, many adult childhood cancer survivors do not meet current lifestyle recommendations and rarely receive structured, tailored support to change health behaviors.

The Behavioral Reinforcement Intervention for Greater Health Trajectories (BRIGHT) study aims to evaluate whether a person-centered, remotely delivered lifestyle intervention can improve health-related quality of life and key health markers in adult survivors of childhood cancer with an unhealthy lifestyle. The intervention focuses on increasing physical activity and improving dietary habits through structured video-based coaching delivered by trained health promoters over a 26-week period.

BRIGHT is conducted within NOPHO-CARE Sweden, a national population-based cohort of childhood cancer survivors, and uses a register-based randomized controlled design with two randomization steps. First, eligible participants are randomized to be offered the intervention or not, enabling evaluation of the population-level effect of offering the intervention through long-term register-based follow-up. Second, participants who consent to active participation are randomized to immediate or delayed start of the intervention, allowing controlled assessment of short-term intervention effects.

The primary research question is whether the BRIGHT lifestyle intervention leads to a clinically meaningful improvement in health-related quality of life, measured by the PROPr utility index derived from PROMIS-29, compared with a control period. Secondary questions address whether the intervention improves physical activity, cardiorespiratory fitness, muscle strength, diet quality, body weight, blood pressure, and cardiometabolic and biological markers, including epigenetic age acceleration. The study also examines feasibility, adherence, and scalability of delivering a person-centered lifestyle intervention within a national survivorship follow-up structure.

In addition, BRIGHT investigates whether offering the intervention to the full eligible population leads to long-term reductions in cardiovascular disease, metabolic disease, psychiatric morbidity, and mortality, using national health registers. By combining individual-level efficacy and population-level effectiveness within a single study framework, BRIGHT aims to generate robust evidence to inform future preventive care and long-term follow-up strategies for adult survivors of childhood cancer.

Survival after childhood cancer has improved substantially, resulting in a growing population of adults exposed to cancer treatment early in life. Adult survivors of childhood cancer are at markedly increased risk of long-term adverse health outcomes, including cardiovascular disease, cardiometabolic disorders, psychological morbidity, and reduced health-related quality of life (HRQoL). While treatment-related factors contribute to these risks, modifiable lifestyle behaviors-particularly physical activity, diet, and body weight-play a central role in shaping long-term health trajectories. Evidence indicates that healthy lifestyle behaviors may yield even greater absolute risk reduction in childhood cancer survivors than in the general population. However, many survivors do not meet recommended lifestyle guidelines and are rarely offered structured, tailored, and sustained behavioral support within routine follow-up care.

The Behavioral Reinforcement Intervention for Greater Health Trajectories (BRIGHT) study is designed to evaluate a person-centered, remotely delivered lifestyle intervention targeting physical activity and dietary habits in adult survivors of childhood cancer with an unhealthy lifestyle. The study is embedded within NOPHO-CARE Sweden, a national population-based survivorship cohort that integrates registry data, patient-reported outcomes, and biological samples. This infrastructure enables both short-term evaluation of intervention efficacy and long-term assessment of population-level effectiveness using national health registers.

Study Design Overview BRIGHT is a pragmatic, register-based randomized controlled trial employing a two-step randomization design to simultaneously address efficacy and real-world effectiveness. The first randomization occurs at the population level within NOPHO-CARE Sweden, where eligible individuals are randomized to be offered the intervention or not. This allows evaluation of the long-term health impact of offering a lifestyle intervention at scale, independent of individual uptake, using register-based follow-up.

The second randomization occurs among participants who consent to active participation in the intervention and study-specific assessments. These participants are randomized to immediate or delayed (waitlist) start of the intervention. This design enables controlled comparisons of short-term intervention effects while ensuring that all actively participating individuals eventually receive the intervention.

Study Population The study targets adult (≥18 years) survivors of childhood cancer who are participants in NOPHO-CARE Sweden and report an unhealthy lifestyle, defined as insufficient physical activity and/or overweight or obesity. Individuals with established cardiovascular disease or other medical conditions that would make participation unsafe are excluded from active participation. Eligibility is determined using existing cohort data and baseline assessments.

Intervention The BRIGHT intervention consists of a structured, person-centered lifestyle coaching program delivered entirely through video-based sessions. Participants engage in 16 scheduled sessions over a 26-week period with trained health promoters who have expertise in behavioral science and lifestyle change. Sessions are conducted weekly during the initial phase of the intervention and biweekly thereafter.

The intervention focuses on supporting participants to increase physical activity and improve dietary habits in line with international recommendations. Using a person-centered approach, participants and health promoters collaboratively identify individualized goals, barriers, and facilitators, and regularly review progress. The intervention emphasizes sustainable behavior change rather than short-term performance targets and is tailored to each participant's preferences, capacities, and life circumstances. The intervention does not include pharmacological treatment or medical decision-making and does not replace or modify routine healthcare.

Data Collection and Assessments Study-specific assessments are conducted remotely and primarily in participants' home environments, with guidance and oversight provided via video visits by research nurses. Assessments are performed at baseline, at follow-up points aligned with intervention timing, and at longer-term follow-up for trajectory analyses.

Data collection integrates:

• Patient-reported outcomes, including health-related quality of life and lifestyle behaviors;
• Objective measurements of physical activity, fitness, body composition, and blood pressure;
• Functional performance tests conducted under video supervision;
• Self-collected capillary blood samples for laboratory analyses of cardiometabolic and biological markers.

All methods used are validated, low-risk, and suitable for remote administration. Standardized protocols and quality control procedures are applied to ensure data reliability.

Outcomes and Follow-up The primary objective of BRIGHT is to determine whether participation in the lifestyle intervention results in a clinically meaningful improvement in health-related quality of life compared with a control period. Secondary objectives address changes in physical activity, fitness, diet, cardiometabolic risk factors, and biological markers, as well as sustainability of effects over time.

Beyond individual-level outcomes, BRIGHT evaluates the long-term effectiveness of offering the intervention at the population level. Participants randomized in the first step are followed longitudinally through national health registers to assess incidence of cardiovascular disease, metabolic disease, psychiatric morbidity, healthcare utilization, and mortality. This approach enables evaluation of whether implementing a lifestyle intervention within a national survivorship follow-up structure translates into meaningful reductions in long-term disease burden.

Feasibility and Scalability An additional objective of BRIGHT is to assess feasibility, adherence, and scalability of delivering a person-centered lifestyle intervention within a national cohort. Metrics such as uptake, retention, adherence to intervention sessions, and completion of assessments are examined to inform future implementation. By embedding the trial within NOPHO-CARE Sweden, BRIGHT evaluates delivery under real-world conditions rather than in a highly selected research setting.

Safety and Ethical Considerations BRIGHT is designed as a minimal-risk behavioral intervention. Physical assessments are conducted under professional supervision via video, with predefined safety criteria and procedures for managing abnormal findings. Participants with clinically concerning measurements are advised to seek routine medical care, but no clinical treatment decisions are made within the study.

All data are pseudonymized and stored in secure research environments in accordance with national and European data protection regulations. Analyses are conducted within protected systems that prevent export of individual-level data. Results are reported only in aggregate form.

Significance BRIGHT is the first national register-based randomized controlled trial in Sweden to evaluate a fully remote, person-centered lifestyle intervention in adult survivors of childhood cancer. By combining individual-level efficacy evaluation with population-level effectiveness assessment, the study aims to generate robust evidence to inform preventive strategies and long-term follow-up care. If successful, BRIGHT may provide a scalable model for integrating structured lifestyle support into survivorship care for childhood cancer survivors at the national level.

Inclusion Criteria:

• Participant in NOPHO-CARE Sweden
• Performing <150 min moderate-vigorous physical activity per week and/or body mass index 28-35.

Exclusion Criteria:

• Pre-existing diagnosis of heart failure or coronary artery disease
• Uncontrolled hypertension, defined as >180/100 mmHg
• Other medical reasons that the intervention or outcome assessments are considered unsafe (as decided by a study physician)
• Inability to perform the intervention or outcome assessments due to lack of mobile device (computer, tablet or telephone) with internet access or language barriers.

Not decided yet.