--- title: Korea's stool test cuts colorectal cancer death — between 50 and 74. Past 80 the association reverses publication: Medical Insights Korea section: news category: Screening canonical_url: https://medicalinsightskorea.com/news/korea-colorectal-screening-fit-works-until-it-does-not author: Chloe Moon published: 2026-09-18T09:00:00+09:00 modified: 2026-09-18T09:00:00+09:00 content_type: reporting license: Quotation permitted with attribution to Medical Insights Korea and a link to the canonical URL. --- # Korea's stool test cuts colorectal cancer death — between 50 and 74. Past 80 the association reverses In a cohort of 5.9 million Koreans, ever being screened carried an odds ratio of 0.74 for colorectal cancer death. The authors report the opposite result in the oldest group, and recommend an upper age limit. ## Answer In a nested case-control study within the Korean National Cancer Screening Program, drawn from a cohort of 5,944,540 colorectal cancer-free individuals aged 50 and over as of 2004, people who had ever been screened with a faecal immunochemical test had an odds ratio of 0.74 (95% CI 0.71 to 0.76) for colorectal cancer-specific mortality, with mortality falling as the number of screens rose — but the effect was not statistically significant at ages 75 to 79 and ran in the opposite direction in people aged 80 and over, leading the authors to recommend the test for ages 50 to 74. ## Key takeaways - The cohort comprised 5,944,540 colorectal cancer-free individuals aged 50 and over as of 2004, with 29,992 deaths after colorectal cancer diagnosis analysed as cases against matched controls. - Ever having been screened carried an odds ratio of 0.74 (95% CI 0.71 to 0.76) for colorectal cancer-specific mortality compared with never being screened. - Colorectal cancer mortality fell further as the number of screens increased. - Results were similar across ages 50 to 79, but were not statistically significant in the 75-to-79 band. - In people aged 80 and over the results ran in the opposite direction. - The authors conclude that faecal immunochemical test mass screening is effective for ages 50 to 74 and recommend that range to countries introducing national colorectal screening. - Korea has offered faecal immunochemical testing to people aged 50 and over through its National Cancer Screening Program since 2004. ## Full article Whether a stool test reduces deaths from colorectal cancer has been argued for years, largely because the randomised trials that exist used an older and less sensitive test. Korea has been offering the modern version to everyone over 50 since 2004, which makes its records the largest available answer. ### What the national data show A study in Cancers used a nested case-control design within the National Cancer Screening Program database. The cohort was 5,944,540 people aged 50 and over who were free of colorectal cancer in 2004. Cases were the 29,992 individuals who died after a colorectal cancer diagnosis; controls were matched on sociodemographic characteristics. **0.74** — odds of colorectal cancer death in Koreans ever screened with a faecal immunochemical test, against never screened (95% CI 0.71–0.76) _Source: Lee HJ et al., Cancers, 2024_ Mortality fell further as the number of screens rose — the same dose-response pattern that gives the gastric endoscopy finding its strength, and for the same reason. A confounder based on who chooses to attend screening does not naturally produce a gradient by how often they attended. ### Where the benefit stops The result held across the 50-to-79 range, but not evenly. In the 75-to-79 band it was no longer statistically significant. In people aged 80 and over, the authors report the opposite result. > **Why screening can stop helping, and then start hurting** > A screening test earns its benefit over years: it finds a cancer early enough that treating it changes when the patient dies. Somebody with a short remaining life expectancy may not live long enough for that benefit to arrive, while the costs — colonoscopy after a positive result, complications of investigation, treatment of a cancer that would never have surfaced — arrive immediately. That is the standard explanation for the pattern, and this study reports the pattern rather than testing the explanation. The authors' recommendation is explicit: the test is effective for ages 50 to 74, and they suggest countries introducing national colorectal screening adopt that range. Korea's own programme begins at 50 and does not stop. ### How this sits with the rest of the bundle The faecal immunochemical test is one of the components of a Korean checkup with genuine mortality evidence behind it, alongside upper endoscopy and mammography. It is also cheap, involves no radiation and no sedation, and its main harm is indirect — the colonoscopies that follow a positive result, most of which find no cancer. That combination is what a well-evidenced screening test looks like, and it is worth stating precisely because so much of what is sold alongside it is not. The argument of this series is not that screening is futile. It is that a package mixes components of very different quality, and this is one of the good ones — inside a defined age range that the package itself does not enforce. ### The limits of the design This is observational. Matching on sociodemographic characteristics does not remove differences in health, comorbidity or health-seeking behaviour between people who attend screening and people who do not, and in the oldest group those differences are likely to be largest — an 80-year-old who attends a screening appointment is not a random 80-year-old. The reversal above 80 should therefore be read as a warning that the benefit is not established at that age, rather than as a measurement of harm. What the study establishes firmly is the middle of the range. Between 50 and 74, in nearly six million people, Koreans who used the stool test were about a quarter less likely to die of colorectal cancer, and more screens meant fewer deaths. ## Sources - Lee HJ, Lee K, Kim BC, Jun JK, Choi KS, Suh M. Effectiveness of the Korean National Cancer Screening Program in reducing colorectal cancer mortality. Cancers 2024;16(24):4278. doi:10.3390/cancers16244278. PMID:39766178. https://doi.org/10.3390/cancers16244278 - Jun JK, Choi KS, Lee HY, Suh M, Park B, Song SH, Jung KW, Lee CW, et al. Effectiveness of the Korean National Cancer Screening Program in reducing gastric cancer mortality. Gastroenterology 2017;152(6):1319-1328.e7. doi:10.1053/j.gastro.2017.01.029. PMID:28147224. https://doi.org/10.1053/j.gastro.2017.01.029 ## Citation Chloe Moon (2026). "Korea's stool test cuts colorectal cancer death — between 50 and 74. Past 80 the association reverses". Medical Insights Korea. https://medicalinsightskorea.com/news/korea-colorectal-screening-fit-works-until-it-does-not Retrieved from https://medicalinsightskorea.com/news/korea-colorectal-screening-fit-works-until-it-does-not