Cohort studyindependent cross-checkabstract checked I-ABX-127 standard review
Very long antibiotic use slightly linked to breast cancer in Korea
Association between Antibiotic Use and Subsequent Risk of Breast Cancer: A Nationwide Retrospective Cohort Study in South Korea.
Overview
Hong J et al.. Cancer Prev Res (Phila) 2025 · PMID 39648494 · DOI 10.1158/1940-6207.CAPR-24-0154
Women with over a year of total antibiotic use had a 15% higher relative risk.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Check antibiotic use and breast cancer in Korea
- How was the study done?
National cohort
- How many people, animals or samples were studied?
4.1 million women
- What was actually found?
Small increase with long use
- How large was the observed effect?
aHR 1.15
- What do the results mean in everyday life?
Small; may reflect other factors
- What are the study's limitations?
Observational
- What does it say about Elawady's specific claim?
Weakly supports an association
- Do the results apply to Germany and Europe?
Low
- What can explicitly not be concluded from this study?
Cause and effect
Scientific in-depth review
1. Full reference
- Authors
- Hong J et al.
- Journal
- Cancer Prev Res (Phila)
- Year
- 2025
- Identifier
- PMID 39648494 DOI 10.1158/1940-6207.CAPR-24-0154
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
National Research Foundation of Korea and Korea Medical Institute (record).
2. Research question
Is antibiotic use associated with breast cancer in Asian women?
3. Study design and population
- Study design
- Cohort study – Nationwide retrospective cohort
- Population
Women in the Korean National Health Insurance database
- Country
South Korea
- Period
2007-2019
- Sample size
4,097,812 women
- Inclusion and exclusion criteria
National insurance data
4. Methods and endpoints
- Exposure / intervention
Cumulative days and number of classes of antibiotics
- Comparator
Non-users
- Endpoints
Incident breast cancer
- Statistical methods
Cox regression
5. Actual results
- Results
>365 days of use aHR 1.15 (95% CI 1.09-1.21); >=5 classes aHR 1.11 (1.05-1.17); cephalosporins aHR 1.09 (1.02-1.17); lincosamides aHR 1.70 (1.20-2.42).
- Absolute risks
not reported
- Authors' conclusion
Long-term use may be associated with higher breast cancer risk; residual confounding must be addressed.
6. Strengths
- Very large
- Duration-response
7. Weaknesses
- Residual confounding (healthcare use, detection)
- Small effect
8. Risk of bias
- Orienting tool
- ROBINS-E
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Detection bias and confounding possible.
9. Assessment of the statistical interpretation
Small relative risk at very long cumulative use.
10. Relevance to the specific claim
Recent supportive data with small effects.
11. Independent contrary findings
Authors call for confirmation of causality.
12. Transferability to Germany and Europe
Low-moderate (Asian population).
13. Overall methodological judgement
Weak support for an association at very high cumulative use.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | inconsistent |
| Regional transferability | low |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Causality.
15. Linked fact checks
- Antibiotic use is associated with breast cancer (archive bibliography). – Studies supporting the claim