Participating in a fecal immunochemical test (FIT) screening program is associated with a decreased incidence of colorectal cancer (CRC) and mortality, according to study findings in Clinical Gastroenterology and Hepatology.
Previous studies revealed that the effect of FIT screening for patients with CRC was unclear. For the current analysis, researchers conducted an observational cohort study to assess the incidence of CRC and mortality between patients who attended an FIT screening vs patients who did not.
The FIT program started in 2005, was delivered by 11 health care district screening units, and targeted over 1,000,000 people aged 50 to 69 years. The regional CRC screening data warehouse provided the data for the study.
Researchers invited eligible patients to participate in a sample FIT every 2 years. Positive results were defined by at least 20 μg hemoglobin/g feces. Patients who tested positive were offered a complete colonoscopy or, in cases of incomplete colonoscopies, a computed tomographic colonography.
There were originally 486,042 men and 495,543 women who received at least 1 invitation. Of these patients, 342,281 men and 365,470 women were considered eligible.
Attenders were patients who responded to the first 2 invitations or responded to the initial invitation before becoming ineligible. Non-attenders were patients who did not respond to the invitations.
Researchers gathered a total of 2,622,131 man-years and 2,887,845 woman-years at risk. In this trial, 4490 men and 3309 women were diagnosed with CRC. For men and women, the proportion of stage I patients was approximately 2 times greater for attenders, and the opposite was observed for stage IV patients.
The yearly incidence rate of CRC peaked in year 1 following the first invitation for attenders of both sexes. The rate subsequently fell and stayed below the rate for non-attenders.
Both sexes showed lower incidence-based CRC mortality rates in attenders compared with non-attenders
The incidence of CRC among men was 35% lower for attenders (95% CI, 0.61-0.69), and women in attendance experienced smaller changes in CRC incidence with an overall decrease of 25% (95% CI, 0.70-0.80). The overall incidence rate ratio (IRR) for both sexes was 0.69 (95% CI, 0.66-0.72).
Overall, self-selection-adjusted IRR increased from 0.65 to 0.67 (95% CI, 0.62-0.72) for men and from 0.75 to 0.79 (95% CI, 0.72-0.88) for women.
Attenders of both sexes showed lower cumulative incidence-based CRC mortality rates than non-attenders. The overall incidence-based mortality rate ratio (MRR) for both sexes was 0.35 (95% CI, 0.31–0.39). Among men, the MMR was 0.32 (95% CI, 0.28- 0.37) and for women was 0.40 (95% CI, 0.34-0.47)
Across the CRC severity stages, the highest IRR was observed for stage I CRC, with 1.35 (95% CI, 1.20-1.50) for men and 1.64 (95% CI, 1.43-1.89) for women.
Study limitations include classifying attendance based on 2 invitations when 5 invitations were sent, a lower prevalence of risk factors in the study population compared to real-world statistics, and differences in all-cause non-CRC-related mortality between attenders and non-attenders.
“The finding that the effect on CRC mortality rates was larger than the effect on incidence was expected,” the study authors wrote. “It clearly indicates that FIT screening prevents deaths both through the removal of high-risk adenomas and through effective treatment of earlier screen-detected invasive CRCs.”
Baldacchini F, Bucchi L, Giuliani O, et al. Effects of attendance to an organized fecal immunochemical test screening program on the risk of colorectal cancer: an observational cohort study. J Clin Gastroenterol Hepatol. 2022;20(10):2373-2382. doi:10.1016/j.cgh.2022.01.053