---
title: One national programme offered two gastric cancer tests. Only one of them changed who died
publication: Medical Insights Korea
section: news
category: Screening
canonical_url: https://medicalinsightskorea.com/news/korea-endoscopy-works-barium-series-does-not
author: Chloe Moon
published: 2026-09-12T15:00:00+09:00
modified: 2026-09-12T15:00:00+09:00
content_type: reporting
license: Quotation permitted with attribution to Medical Insights Korea and a link to the canonical URL.
---

# One national programme offered two gastric cancer tests. Only one of them changed who died

In 16.6 million Koreans, upper endoscopy carried an odds ratio of 0.53 for gastric cancer death. The barium series offered alongside it carried 0.98. The gap widened with every repeat endoscopy.

## Answer

Within the Korean National Cancer Screening Program, which offers people aged 40 and over either upper endoscopy or an upper gastrointestinal series, a nested case-control study of a cancer-free cohort of 16,584,283 people found that endoscopy was associated with an odds ratio of 0.53 (95% CI 0.51 to 0.56) for death from gastric cancer while the upper gastrointestinal series was associated with 0.98 (95% CI 0.95 to 1.01), and the endoscopy effect strengthened with repetition — 0.60 after one screen, 0.32 after two and 0.19 after three or more.

## Key takeaways

- A nested case-control study within the Korean National Cancer Screening Program drew on a cancer-free cohort of 16,584,283 men and women aged 40 and over, with 54,418 gastric cancer deaths as cases and 217,672 matched controls.
- Ever having been screened carried an odds ratio of 0.79 (95% CI 0.77 to 0.81) for death from gastric cancer.
- Split by method, upper endoscopy carried an odds ratio of 0.53 (95% CI 0.51 to 0.56) and upper gastrointestinal series 0.98 (95% CI 0.95 to 1.01).
- The endoscopy effect strengthened with repetition: 0.60 after one screen, 0.32 after two, and 0.19 after three or more.
- A separate cohort of 15,850,288 people found that a negative screen was followed by lower upper gastrointestinal cancer mortality in both groups, but far more so after endoscopy — hazard ratio 0.21 against 0.55 for the barium series.
- In that cohort the largest reductions were seen in people aged 60 to 69, where a negative endoscopy carried a hazard ratio of 0.19 for upper gastrointestinal cancer death.

## Full article

Korea launched national gastric cancer screening in 1999, offering everyone aged 40 and over a choice between two tests every two years: upper endoscopy, or an upper gastrointestinal series done with barium and X-rays. Both were in the programme. Both were paid for. Eighteen years of national data show that only one of them was doing anything.

### The comparison the programme accidentally ran

A study published in Gastroenterology used the programme's own records as a natural experiment. From a cancer-free cohort of 16,584,283 people, it identified 54,418 individuals newly diagnosed with gastric cancer between 2004 and 2009 who died before December 2012, and matched each to four controls alive on the date the case died, matched on year of entry, age, sex and socioeconomic status.

**Odds of death from gastric cancer, by screening method**

| Exposure | Odds ratio (95% CI) |
| --- | --- |
| Ever screened, any method | 0.79 (0.77–0.81) |
| Upper endoscopy | 0.53 (0.51–0.56) |
| Upper gastrointestinal series | 0.98 (0.95–1.01) |

An odds ratio of 0.98 with a confidence interval from 0.95 to 1.01 is not a weak effect. It is the absence of one, measured precisely, in a national programme that offered the test for eighteen years.

### The pattern that argues this is causal

The obvious objection to any observational screening study is that people who attend screening are different from people who do not — healthier, wealthier, more health-conscious — and that the difference, not the test, produces the result. The strongest evidence against that reading here is not a statistical adjustment. It is the shape of the endoscopy result.

- One endoscopic screen: odds ratio 0.60 (95% CI 0.57 to 0.63).
- Two: 0.32 (0.28 to 0.37).
- Three or more: 0.19 (0.14 to 0.26).

Health-conscious attendance would be expected to raise both figures together. Instead the benefit deepens with each additional endoscopy while the barium series stays at unity no matter how often it is repeated. A confounder that produces a dose-response in one arm of the same programme and none in the other would have to be a very unusual confounder.

**0.19** — odds of death from gastric cancer after three or more endoscopic screens, against never being screened  
_Source: Jun JK et al., Gastroenterology, 2017_

### What a clear scan is worth

A second national cohort, of 15,850,288 people followed to 2017 for cancer and 2019 for death, asked a different question: what does a negative screening result predict? Over that period it recorded 230,783 upper gastrointestinal cancers and 99,348 deaths from them.

**After a negative screen: adjusted hazard ratios**

|  | Upper GI cancer | Upper GI cancer death |
| --- | --- | --- |
| Negative upper endoscopy | 0.67 (0.67–0.68) | 0.21 (0.21–0.22) |
| Negative upper GI series | 0.81 (0.80–0.82) | 0.55 (0.54–0.56) |

Both negative results carry reassurance. A clear endoscopy carries much more of it. The largest reductions in both studies fell in the 60-to-69 age band, where a negative endoscopy was followed by a hazard ratio of 0.19 for upper gastrointestinal cancer death.

### What this settles and what it does not

These are observational analyses of a national programme, not randomised trials, and neither can fully exclude that the people choosing endoscopy differed from those choosing barium in ways the matching did not capture. What makes the comparison unusually strong is that both groups were inside the same programme, invited the same way, at the same intervals, for the same disease.

Neither study measures the harms of endoscopy — perforation, bleeding, sedation events, or the consequences of findings that would never have caused illness. A test that halves gastric cancer mortality is not thereby free, and the studies that would quantify what it costs are not these.

For somebody reading a checkup package, the practical content is narrow and firm. Where a Korean programme offers a choice between endoscopy and a barium upper gastrointestinal series for gastric cancer, the national data say those are not two versions of the same test.

## Sources

- 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
- Luu XQ, Lee K, Jun JK, Suh M, Jung KW, Choi IJ, Choi KS. Risk of upper gastrointestinal cancer and death in persons with negative screening results: results from the National Cancer Screening Program in South Korea. Gastric Cancer 2023;26(4):580-589. doi:10.1007/s10120-023-01387-0. PMID:37020074. https://doi.org/10.1007/s10120-023-01387-0
- Krogsbøll LT, Jørgensen KJ, Gøtzsche PC. General health checks in adults for reducing morbidity and mortality from disease. Cochrane Database of Systematic Reviews 2019;1:CD009009. doi:10.1002/14651858.cd009009.pub3. PMID:30699470. https://doi.org/10.1002/14651858.cd009009.pub3

## Citation

Chloe Moon (2026). "One national programme offered two gastric cancer tests. Only one of them changed who died". Medical Insights Korea. https://medicalinsightskorea.com/news/korea-endoscopy-works-barium-series-does-not

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