Colorectal cancer (CRC) is a major health burden. Screening can reduce both incidence and mortality of CRC. Endoscopic screening with sigmoidoscopy or colonoscopy and testing for occult blood in stool are the most frequently applied methods, but the comparative effectiveness is unknown. Effectiveness of screening depends on the test used, but also on high participation in screening. Anticipation of pain can jeopardize participation in endoscopic screening programmes. Women have a higher risk of painful colonoscopies than men. The absence of bowel symptoms may be another barrier to screening participation, as asymptomatic individuals show a lower adherence to screening programmes.
The present thesis is based on data from a Norwegian randomised CRC screening trial. About 140.000 individuals were invited to either sigmoidoscopy or repeated faecal immunochemical tests (FIT).
The results showed that the participation rate in FIT screening was higher than in sigmoidoscopy screening. More CRCs and advanced adenomas were detected at FIT screening and most of the neoplasia were detected in asymptomatic screening participants. Women receiving analgesia prior to colonoscopy reported fewer painful colonoscopies than women treated with analgesia on-demand.
The comparative effectiveness of sigmoidoscopy and FIT screening is unknown until results from long-term follow-up are available. Nevertheless, the present thesis provides important information about planning and implementing a colorectal cancer screening programme. The results highlight the importance of encouraging asymptomatic individuals to participate in screening programmes. It was also shown that analgesia should be offered to women before colonoscopy starts. Optimized pain relief during colonoscopy may have impact on the reputation of screening and thus increase participation rates and effectiveness of endoscopic screening.