Effectiveness of Colorectal Cancer Screening in Detecting Earlier-Stage Disease-A Nationwide Cohort Study in Denmark.

BACKGROUND & AIMS: Most studies of the effectiveness of screening for colorectal cancer (CRC) using the fecal occult blood test tested the guaiac fecal occult blood test. However, the fecal immunochemical test (FIT) is now commonly used in screening. We aimed to evaluate the effectiveness of FIT-based screening for CRC on the number of incident CRC diagnoses and stage at diagnosis for individuals in Denmark who were invited for screening vs not yet invited.

METHODS

We collected data for this register-based retrospective cohort study during the first 16 months of the prevalence round of a FIT-based CRC screening program (March 1, 2014 through June 30, 2015). A total of 402,826 residents of Denmark (50-72 years old) were randomly invited to undergo CRC screening within the study period, and 956,514 were invited thereafter. We obtained information on CRC diagnosis, date, and stage at diagnosis from the Danish Colorectal Cancer Group database. Cancer incidence per 100,000 invited/not yet invited individuals was calculated, along with the relative risk (RR) of CRC among invited compared with not yet invited individuals.

RESULTS

CRC incidence during the study period was 339.4/100,000 invited individuals and 169.6/100,000 not yet invited individuals. CRC incidence increased with age among invited and not yet invited individuals. For invited women compared with not yet invited women, the RR of being diagnosed with stage I CRC was 3.39 (95% CI, 2.61-4.39), with stage II CRC was 2.16 (95% CI, 1.71-2.72), with stage III CRC was 1.37 (95% CI, 1.08-1.75), and with stage IV CRC was 0.92 (95% CI, 0.68-1.23). For invited men compared with not yet invited men, the RR of being diagnosed with stage I CRC was 3.71 (95% CI, 2.97-4.64); with stage II CRC was 2.26 (95% CI, 1.84-2.77), with stage III CRC was 1.88 (95% CI, 1.53-2.30), and with stage IV CRC was 1.20 (95% CI, 0.95-1.52).

CONCLUSIONS

In analyzing data from a register-based cohort study in Denmark, we found that inviting individuals to undergo FIT-based CRC screening led to detection of almost 2-fold more cases of CRC than not inviting participants. The significant increase of CRC incidence among those invited for screening indicates a need for awareness of treatment capacity in countries introducing FIT-based CRC screening.