Growth trajectories and risk of underweight and overweight in childhood cancer patients and survivors: a longitudinal multicentre cohort study protocol

Background: Underweight, overweight, and linear growth during and after cancer treatment can impact treatment efficacy and survival in childhood cancer patients, and long-term health in childhood cancer survivors (CCS). However, scientific evidence on the weight status and growth of CCS is limited. Previous studies have been small, focused on specific cancer types, or lacked objectively measured longitudinal data. The availability of standardized, semantically interoperable routine data from oncology clinics offers an unprecedented opportunity to investigate nutritional status across all childhood cancer types, treatment regimens, and critical time windows. Objectives: We will investigate underweight, overweight, and growth trajectories from birth to adulthood in childhood cancer patients and survivors. We will identify predictors associated with distinct growth and weight trajectories and assess the consistency of findings across European countries. Methods: The Growth study will collect routinely recorded sociodemographic, clinical, and anthropometric data from paediatric and adolescent cancer patients (aged <20 years) from Switzerland, Portugal and Slovenia, We will include patients diagnosed between 2004-2026, by linking data from the Swiss Childhood Cancer Registry (ChCR), the Swiss Childhood Cancer Survivor Study (SCCSS), the Swiss Federal Statistical Office (FSO), and oncology clinics in Switzerland. Deterministic linkage of data sources (ChCR, SCCSS, oncology clinics, and FSO) will be performed using social security numbers. We will calculate age- and sex-specific z-scores for weight, height, and BMI based on country-specific and World Health Organization growth references. Latent trajectory modelling will be applied to identify distinct growth and weight trajectories and to detect subgroups at increased risk of growth impairment. We will use logistic regression models to identify predictors of impaired growth. Results: The project was funded in 2025; first study results are expected to be published by autumn 2027. We will obtain routinely collected data from approximately 12,250 childhood cancer patients and survivors - 7,800 from Switzerland, 3,350 from Portugal, and 1,100 from Slovenia. Conclusions: The Growth study will provide insights into the nutritional status of childhood cancer patients and survivors and improve understanding of growth patterns in this population. Identifying high risk groups and tumour or treatment related factors will inform targeted surveillance strategies and early nutritional interventions.