Underweight, Overweight, and Linear Growth of Childhood Cancer Patients - the Growth Study

Background: Underweight, overweight, and obesity occur frequently after childhood cancer diagnosis, and are common during and after cancer treatment. Childhood is a critical period for growth and development, which can be disrupted by cancer, treatment side effects, and increased physical demands. Poor nutritional status before and during treatment can in turn lead to complications, including infections, treatment-related toxicities, and reduced survival. However, scientific evidence on weight status and growth trajectories in childhood cancer patients and survivors remains limited. Previous studies have been small, focused on specific cancer types, or lacked objectively measured longitudinal data.

Electronic health records (EHRs) are routinely collected during clinical visits in hospitals. They provide an opportunity for clinical research, as they guarantee repeated and reliable records of clinically relevant factors, such as height, weight, and treatments received. In many European countries, such as Switzerland, Portugal, and Slovenia, hospitals and clinical data warehouses are making EHRs available and linkable to additional data sources (e.g., registries) via unique identifiers. The availability of standardized, semantically interoperable routine data from paediatric hospitals offers an unprecedented opportunity to investigate nutritional status across all childhood cancer types, treatment regimens, and critical time windows.

Objectives: The study will investigate nutritional status, body mass index (BMI), and linear growth trajectories from birth to adulthood in childhood cancer patients and survivors. It 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 children and adolescents cancer patients (aged <20 years) 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, Portugal, and Slovenia. Deterministic linkage of data sources (ChCR, SCCSS, and oncology clinics) and probabilistic linkage with FSO data using patients' names, sex, and age will be performed.

The investigators will calculate age- and sex-specific z-scores for weight, height, and BMI based on country-specific and World Health Organization growth references. Group-based trajectory modelling will be applied to identify distinct growth and weight trajectories and to detect subgroups at increased risk of growth impairment. The investigators will use multinomial logistic regression models to identify predictors of impaired growth.

Rationale and significance: 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. By providing a comprehensive overview of BMI and growth patterns and their predictors across different cancer types, this study will identify tumours, treatments, and critical time windows of concern. Identifying high risk groups and tumour- or treatment-related factors will facilitate cross-country comparisons and inform targeted surveillance strategies and early nutritional interventions.

Current status (07.2026): The investigators expect to obtain routinely collected data from approximately 12,150 childhood cancer patients and survivors - 7,450 from Switzerland, 3,750 from Portugal, and 950 from Slovenia.

Funding: Swiss Cancer Research (KFS-6351-02-2025-R) and the Swiss National Science Foundation (SNSF, 10.007.011).

Inclusion criteria

• Diagnosed with cancer at age <20 years
• Diagnosed between 2004 and 2026
• Treated in one of the participating cancer centres:

• Switzerland: patients who visited one of the cancer centres in Switzerland: Aarau, Basel, Bellinzona, Bern, Geneva, Lausanne, Lucerne, St. Gallen, Zurich.
• Portugal: patients diagnosed between 2012-2026 at the Portuguese paediatric oncology centres Instituto Português de Oncologia do Porto Francisco Gentil - IPO-PORTO or at the Instituto Português de Oncologia Francisco Gentil - IPOLFG.
• Slovenia: patients diagnosed between 2011-2026 at the paediatric oncology clinic University Medical Center Ljubljana.