The COLON study: Colorectal cancer: Longitudinal, Observational study on Nutritional and lifestyle factors that may influence colorectal tumour recurrence, survival and quality of life

Design and population: Prospective, multicenter, observational cohort enrolling at least 1,000 incident colorectal cancer patients diagnosed at 11 hospitals in the Netherlands. Eligibility: men and women of all ages with newly diagnosed colorectal cancer (ICD C18-20). Exclusions: non-Dutch speakers; history of colorectal cancer or (partial) bowel resection; chronic inflammatory bowel disease; hereditary colorectal cancer syndromes; dementia or other conditions that prevent questionnaire completion. Data collection: questionnaires at diagnosis, 6 months, 2 years, 5 years; blood samples at each timepoint; optional paraffin-embedded tumor material; diagnostic CT scans to assess body composition; fecal samples in colon cancer subgroup; data linkages with the Netherlands Cancer Registry and municipal databases. Outcomes: treatment completion rates, treatment-related side-effects, disease outcomes including recurrence and mortality, and quality of life. Analyses: Cox models for associations between dietary and lifestyle factors at diagnosis and recurrence/survival; repeated-measures analyses for changes over time; adjustments for age, sex, and stage; sample size ~1,000; expected events ~320 recurrences and ~250 deaths over 5 years.

Not results yet; aims to determine whether diet and lifestyle factors, including dietary supplement use, body composition, nutrient status (e.g., vitamin D), and gut microbiota, influence colorectal cancer recurrence, survival, and quality of life. With ~1,000 participants and up to 5 years of follow-up, findings could inform evidence-based dietary and lifestyle recommendations for colorectal cancer patients.