Cancer Screening in Korea: Does Finding It Earlier Actually Save Lives?
Medical Korea recently shared a striking statistic about cancer outcomes in South Korea.
Korea recorded the lowest mortality-to-incidence ratios for stomach, colorectal, and breast cancer among the major countries compared in Korea's latest national cancer statistics.
The numbers are impressive:
Source: Medical Korea
Source: Medical Korea
In simple terms, the mortality-to-incidence, or M/I, ratio compares the number of people who die from a cancer with the number diagnosed with it. Korea's latest national cancer report found that these three ratios were the lowest among the major countries compared, including the U.S., Japan, the U.K., Germany, Italy and China.
But there is an important limitation.
A Low M/I Ratio Doesn't Prove Better Screening
Countries that screen more people simply find more cancer — including small, slow-growing tumors that would never have caused symptoms. That is overdiagnosis, and it enlarges the denominator. The ratio improves while the same number of people die.
The U.S. National Cancer Institute makes the point directly: because of overdiagnosis and lead-time bias, screening can improve survival rates and increase the number of cancers found at an early stage without reducing cancer deaths.
One more caveat. The Medical Korea graphic cites GLOBOCAN 2022 and its 185 countries, but the Korean report compares Korea against six: the U.S., Japan, the U.K., Germany, Italy and China. Korea's figures are 2023 national data; the others are 2022 estimates.
So the ratio caught our attention. We wanted to look one level deeper. Are cancers actually being found earlier? And are fewer people dying from them?
More Cancer Is Being Found Before It Spreads
The change over the past two decades is significant.
As screening became much more common, the share of stomach, colorectal, and breast cancers diagnosed while still localized also increased substantially. Across all cancers, localized-stage diagnoses rose from 45.6% in 2005 to 51.8% in 2023.
That is encouraging—but it still does not completely solve the overdiagnosis question. The harder test is mortality.
Are Fewer People Actually Dying?
Across all cancers, Korea's age-standardized cancer mortality rate fell 44.2% between 1999 and 2023, from 115.1 to 64.3 per 100,000. Mortality from stomach and colorectal cancer declined substantially during this period. More importantly, nationwide studies of Korea's screening programs have looked directly at cancer-specific deaths.
- STOMACH CANCER 47% lower odds of dying from stomach cancer among people screened by endoscopy versus those never screened 16.6 million-person cohort
- COLORECTAL CANCER 26% lower odds of colorectal-cancer death among people screened by fecal immunochemical test versus those never screened 5.9 million-person cohort
- BREAST CANCER 22% estimated reduction in breast-cancer mortality among screened women ages 40–69 after adjustment for self-selection bias 8.3 million women
The gastric cancer study found an odds ratio of 0.53 for endoscopic screening — notably, the same study found no benefit for barium upper-GI series, so the method mattered, not merely the act of being screened. The colorectal study reported an odds ratio of 0.74 among adults aged 50 and older. The breast cancer study followed 8.3 million women aged 40–79 and estimated a 22.08% net mortality reduction among those aged 40–69 after adjusting for self-selection bias.
These are observational studies, not randomized trials, so screening alone cannot be credited for every improvement. Better treatments, changes in risk factors, and differences between people who choose to be screened and those who do not also matter. But mortality is much harder to explain away with overdiagnosis alone.
Korea's Advantage Isn't Simply "More Testing"
To me, that's the more interesting story. The strongest argument for Korea's preventive healthcare system isn't that Koreans undergo more tests.
It is that Korea has built an infrastructure where organized screening happens at population scale, participation is high, and a growing share of major cancers are being found before they spread. Korea's national screening rates for stomach, colorectal, and breast cancer have all risen dramatically over the past two decades.
And importantly, those changes have occurred alongside declining cancer mortality. For American patients, that distinction matters. More testing is not always better. Screening should still reflect age, family history, personal risk and the evidence behind each test. The lesson from Korea is not to test for everything. It is to make the right early detection easier to access.
At Himedi, we think the best health checkup isn't the one with the longest list of tests. It's the one that helps you understand your risks and decide what to do next.
About the Author
Donkyo Seo Co-founder & CEO, Himedi
For the past 9 years, Donkyo has helped international patients navigate Korean healthcare. Himedi is licensed by Korea's Ministry of Health & Welfare (License #A-2016-01-01-2345).
Sources
- Park EH, Jung KW, Choi SH, et al. "Cancer Statistics in Korea: Incidence, Mortality, Survival, and Prevalence in 2023." Cancer Research and Treatment, 2026;58(2):349–367. doi:10.4143/crt.2026.298 — M/I ratios and six-country comparison (Fig. 8), screening rates, stage distribution, mortality trend.
- National Cancer Institute. "Crunching Numbers: What Cancer Screening Statistics Really Tell Us" and "Cancer Screening Overview (PDQ) — Health Professional Version." cancer.gov — overdiagnosis, lead-time bias.
- Jun JK, Choi KS, Lee HY, 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
- 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
- Choi E, Jun JK, Suh M, et al. "Effectiveness of the Korean National Cancer Screening Program in reducing breast cancer mortality." npj Breast Cancer, 2021;7(1):83. doi:10.1038/s41523-021-00295-9
