The association of reduced colorectal cancer risk with colonoscopy or fecal immunochemical testing (FIT) was stronger for distal colorectal cancer vs proximal. As FIT assessment frequency increased, the association with colorectal cancer prevention also increased in strength. The results of this study were published in Clinical and Translational Gastroenterology.
This population-based, case-control study used claims data regarding colonoscopy and FIT from the Korean National Health Insurance System. The case group consisted of 61,221 patients with newly diagnosed colorectal cancer while 306,099 individuals without colorectal cancer comprised the age and sex matched control group.
In the case group, colorectal cancer occurred most often in the distal location (67.5%). The number of patients undergoing colonoscopy in the case vs control groups were 5686 (9.3%) and 77,476 (25.3%), respectively, while 25.2% of patients with cancer and 32.3% of controls underwent FIT.
The adjusted odds ratio (aOR) of any colonoscopy for all colorectal cancer compared with no colonoscopy was 0.29 (95% CI, 0.28-0.30) and the association with cancer prevention was stronger for distal (OR, 0.24; 95%, CI 0.23–0.24) vs proximal cancer (OR, 0.47; 95% CI, 0.44–0.49). When stratifying the analysis by age and sex at diagnosis, the association between colonoscopy and cancer risk was weaker in women (OR, 0.33; 95% CI, 0.31–0.34) and in patients aged 75 years or older (OR, 0.43; 95% CI, 0.40–0.46).
For patients exposed to FIT compared against those without exposure, the risk of developing colorectal cancer was lower (OR, 0.74; 95% CI, 0.73–0.76). The stratified analysis found the association between FIT and cancer risk reduction was weaker in patients aged 75 years or older (OR, 0.94; 95% CI, 0.90–0.99) compared with patients aged 49 years or younger (OR, 0.62; 95% CI, 0.41–0.92) and those aged 50 to 74 years (OR, 0.70; 95% CI, 0.69–0.72). The odds ratio of FIT exposure for colorectal cancer decreased from 0.81 (95% CI, 0.80–0.83) to 0.45 (95% CI, 0.39–0.51) as the frequency of FIT assessments increased from 1 to greater than 5 in the previous 10 years.
The study was limited by a lack of specific colonoscopy details in the claims data and a lack of standardization regarding colonoscopy. The claims data also lacked comprehensive clinical findings for each patient and the limited variables used in the study meant potential confounders could not be addressed. Additionally, the data was not analyzed in detail according to cancer location. Finally, colonoscopy for screening purposes is more common in South Korea than other countries, even for younger people and those with no suspicious findings or medical history, thus reducing the generalizability of the results to other countries.
According to researchers, “These results highlight the importance of active and continuous participation and colonoscopy quality control in [colorectal cancer] screening at the population level.”
Kim SY, Kim H-S, Kim YT, et al. Colonoscopy versus fecal immunochemical test for reducing colorectal cancer risk: a population-based case-control study. Clin Transl Gastroenterol. 2021;12(5):e00350. doi:10.14309/ctg.0000000000000350