Short summary

The ongoing Danish colorectal cancer screening program increases the number of people at risk of developing colorectal cancer (CRC) after receiving a negative reply from their screening-participation, a so-called interval cancer (IC). Interval cancers can occur both after a negative colonoscopy or a negative Fecal Immunochemical Test (FIT). Research on IC after negative colonoscopy has been examined rather extensively, but IC after a negative FIT has so far received relatively little attention. As the number of people at risk of developing FIT-neg. IC increases, the possibility to investigate arises.  We seek to not just examine the incidence of IC, but also to investigate at what FIT levels most ICs occur, providing knowledge that can be used to tailor the screening program by e.g. letting the lowest risk group from the program "skip" a round (or more) of screening resulting in fewer participants adding to less strain on the program and the health sector.

 Due to the extensive registration in both the Danish Colorectal Cancer Database and the Danish Colorectal Cancer screening database, a large set of data will be available to us, containing different covariates e.g. demographics and lifestyle habits (smoking & alcohol consumption) allowing us the opportunity to study their effects on the development of IC CRC.  Lastly we will seek to study the location and type of tumor, leading to a possible discussion on the current standard operations used when examining FIT-pos. participants versus new methods such as the Camera Capsule Endoscopy (CCE). 

Overall, this study aims to investigate the incidence of IC CRC at different FIT-levels in the Danish screening population between 2014 and 2016.