Cohort studyindependent cross-checkabstract checked★ key study I-INS-127 in-depth review
Glargine, prior insulin use and breast cancer
Insulin glargine use and breast cancer risk: Associations with cumulative exposure.
Overview
Peeters PJ et al.. Acta Oncol 2016 · PMID 27150973 · DOI 10.3109/0284186X.2016.1155736
Women starting with glargine had no extra breast cancer even after 5 years; a raised risk appeared only in women with long prior use of other insulins.
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?
Relate glargine duration to breast cancer.
- How was the study done?
UK cohort.
- How many people, animals or samples were studied?
12,468 women.
- What was actually found?
No effect in new users; HR 3.17 in long-term switchers.
- How large was the observed effect?
HR 1.06 (new users >=5 y).
- What do the results mean in everyday life?
Glargine itself is unlikely to be the cause.
- What are the study's limitations?
Few cases.
- What does it say about Elawady's specific claim?
Weakens the breast-cancer claim for glargine.
- Do the results apply to Germany and Europe?
UK data.
- What can explicitly not be concluded from this study?
Cannot explain the switcher signal.
Scientific in-depth review
1. Full reference
- Authors
- Peeters PJ et al.
- Journal
- Acta Oncol
- Year
- 2016
- Identifier
- PMID 27150973 DOI 10.3109/0284186X.2016.1155736
- Verification
- verified – PubMed efetch 2026-10-26; Crossref 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Does breast cancer risk rise with duration of glargine use, accounting for prior insulin?
3. Study design and population
- Study design
- Cohort study – Retrospective cohort (UK CPRD) with time-dependent exposure
- Population
Women with a first insulin prescription
- Country
United Kingdom
- Period
2002-2013
- Sample size
12,468 women; 186 breast cancers
- Inclusion and exclusion criteria
First-ever insulin prescription
4. Methods and endpoints
- Exposure / intervention
Cumulative glargine use
- Comparator
Other insulins
- Endpoints
Breast cancer
- Statistical methods
Cox models; p-trends
5. Actual results
- Results
Insulin-naive women: no association with cumulative glargine use (p-trend 0.91), HR 1.06 (0.48-2.33) after >=5 years. Switchers with >3 years prior other insulin: HR 3.17 (1.28-7.84); non-significant trend with glargine exposure among switchers.
- Absolute risks
not reported
- Authors' conclusion
Glargine was not associated with increased breast cancer risk in insulin-naive patients; prior exposure to other insulins appears relevant.
6. Strengths
- Time-dependent exposure
- Separates new users and switchers
7. Weaknesses
- Few cases
- Wide CIs
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
Small numbers.
9. Assessment of the statistical interpretation
Imprecise; switcher signal may reflect long diabetes/insulin duration rather than glargine.
10. Relevance to the specific claim
Suggests the breast-cancer signal relates to prior long insulin exposure (switchers), not to glargine in new users.
11. Independent contrary findings
12. Transferability to Germany and Europe
Directly applicable; same biology and clinical standards in Europe.
13. Overall methodological judgement
Mixed; weakens the glargine-specific interpretation.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- Insulin glargine increases cancer risk in a dose-dependent way (and long-term use increases breast cancer). – Studies with mixed or unclear results