PhD defence E.F.P. (Elleke) Peterse

Colorectal cancer is one of the leading causes of cancer death, and is an increasing public health concern for many countries worldwide. Screening can prevent colorectal cancer death through removal of premalignant lesions or through early detection of colorectal cancer. The aim of this thesis was to estimate population-level effects of colorectal cancer screening policy changes or interventions.  Our analyses focused on three different policy domains. First, we attempted to optimize colorectal cancer screening guidelines in light of contemporary trends in colorectal cancer screening incidence in the United States. We demonstrated that screening initiation at age 45 years rather than age 50 years has a favorable balance between screening benefits, burden and costs. Furthermore, colorectal cancer screening guidelines need not to be differentiated by race and sex. Second, we evaluated the cost-effectiveness of interventions that potentially increase screening participation. Waiving all out-of-pocket costs for colorectal cancer screening, mailing a stool-based test to individuals eligible for screening, and offering an alternative blood-based test for individuals that otherwise do not want to participate in screening are cost-effective interventions. Third, we focused on improving the detection and clinical management of Lynch syndrome patients. Our analyses suggest that testing colorectal cancer cases for Lynch syndrome, and subsequently testing first-degree relatives of those found to have Lynch syndrome, provides a good balance between costs and long-term benefits. From a cost-effectiveness perspectives, individuals with Lynch syndrome should be advised to undergo colonoscopy surveillance every two years, and women between age 40 and 80 years with Lynch syndrome should  be offered prophylactic hysterectomy.

Due to corona, the PhD defences do not take place publicly in the usual way in the Senate Hall or in the Professor Andries Querido Room. The candidates will defend their dissertation either in a small group or online.