Lay summary
Rates of bowel cancer in younger adults under 50 are rising rapidly in Aotearoa New Zealand and overseas. These younger patients often present with advanced disease, face delays in diagnosis because current guidelines exclude them from urgent colonoscopy, and experience unique challenges such as impacts on fertility, family life and employment. This project will establish the first nationwide study of early-onset colorectal cancer (EOCRC) in Aotearoa New Zealand. We will collect blood, stool and tumour samples, along with lifestyle and health information, to understand why EOCRC is increasing and to identify new risk factors. We will also test simple blood-based biomarkers that could help doctors prioritise younger patients with bowel symptoms for investigation, leading to earlier diagnosis. By combining scientific, clinical and patient perspectives, this research will provide evidence to guide policy, improve services and reduce the personal, social and economic burden of EOCRC.