PhD defence L. (Lucie) de Jonge

Brief summary of the doctoral thesis:

Colorectal cancer (CRC) is a global health problem ranked as the third most common cancer in the world. Screening has proven to decrease CRC incidence and CRC-related mortality through the  removal of precursor lesions and of cancers detected in an early stage. Therefore, many countries have implemented an organized CRC screening program using colonoscopy screening or fecal immunochemical test (FIT) screening.  Using microsimulation and observational data from screening programs, the aim of this thesis is to investigate how to safeguard the (cost-)effectiveness of CRC screening programs. The research consisted of three topics: evaluation and monitoring, CRC screening during COVID-19 and new developments. The first part is comprised of studies with examples and methodologies of evaluating and monitoring CRC screening programs. In the second part, the impact of the COVID-19 pandemic on CRC screening was investigated as many programs were temporarily suspended or operating at restricted capacity. The third part consisted of studies investigating new developments in CRC screening: a new screening test and risk-based screening. Based on the results of this thesis, the authors suggested that in order to safeguard the effectiveness of CRC screening programs, large evaluations of population-based organized CRC screening programs should be conducted to evaluate whether actual outcomes of the program are meeting expectations. Moreover, microsimulation models for CRC should be used to extrapolate (existing) evidence and determine the optimal screening strategy when real-life data is not (yet) available.