Algorithms in colorectal cancer screening

Screening individuals for colorectal cancer (CRC) leads to a reduction in disease-related morbidity and mortality. In Europe, screening is mostly performed using the faecal immunochemical test (FIT). Individuals with a positive FIT result are referred for colonoscopy, where cancer or precursor lesion can be detected and/or resected. FIT is not optimal, as it lacks the ability to accurately detect precursor lesions. Algorithms may improve the yield of screening by combining FIT with other risk factors. The studies in this thesis aimed to develop and evaluate these algorithms while using readily available data that have low additional operational costs, such as age, sex, and data derived from questionnaires. Another drawback of FIT is the high number of individuals who receive a false-positive test. This thesis also describes work on an add-on test designed to reduce the number of individuals undergoing an unnecessary colonoscopy. Finally, this thesis proposes several potential avenues for the development of algorithms in CRC screening.