Weight management in obese cancer patients during curative active treatment: protocol for the CANOBESE feasibility study.

Obesity is highly prevalent among patients with cancer and is associated with increased risks of treatment-related complications, poorer oncological outcomes, and long-term morbidity. Despite this, current oncology nutrition guidelines primarily address malnutrition and provide limited direction for clinical management of patients with obesity. Intentional weight loss interventions during cancer treatment are uncommon, partly due to concerns about safety and feasibility. The CANOBESE study aims to address this evidence gap by evaluating the feasibility of implementing a structured, multimodal weight management programme for patients with obesity undergoing curative oncological treatment.

This single-arm feasibility trial will recruit 50 adult patients with a BMI ≥ 30 kg/m2 and newly diagnosed stage II-IV solid tumours receiving chemotherapy, radiotherapy, immunotherapy, targeted therapy alone, or in combination with curative intent. The intervention includes a personalized hypocaloric and high-protein diet, a supervised home-based aerobic and resistance exercise programme, and integrated behavioural support delivered throughout the programme, with psycho-oncological input when more intensive individualized support is needed. Follow-up will continue for the duration of active treatment (3-9 months). The study will evaluate feasibility by examining key aspects such as recruitment and retention rates, intervention adherence and fidelity, participant acceptability, and the completeness of data collection throughout the intervention period.

Secondary outcomes include exploratory changes in weight, body composition, physical performance, dietary intake, quality of life, and inflammatory biomarkers. The broad eligibility criteria were selected to evaluate feasibility in a pragmatic real-world oncology setting, while predefined exclusions were used to reduce baseline nutritional risk and improve safety. The CANOBESE study represents one of the first efforts to assess whether a comprehensive lifestyle intervention can be effectively delivered to patients with obesity during curative cancer treatment. This protocol incorporates patient and public involvement, a multidisciplinary team approach, and real-world implementation considerations.

Findings will inform the scalability of the intervention, characterize implementation challenges across a pragmatic oncology population, and guide the design of a future randomized controlled trial. The study is not intended to provide subgroup-specific clinical recommendations, but to generate feasibility data that may help refine tailored approaches to intentional weight management in oncology settings. ClinicalTrials.gov identifier: NCT07058207. Registered on 9 July 2025. https://clinicaltrials.gov/study/NCT07058207.