Otherindependent cross-checkabstract checked★ key study I-CAN-130 in-depth review
Most cancer risk comes from outside factors
Substantial contribution of extrinsic risk factors to cancer development.
Overview
Wu S et al.. Nature 2016 · PMID 26675728 · DOI 10.1038/nature16166
Modelling suggests that internal 'bad luck' explains only about 10-30% of lifetime cancer risk; the rest depends on external factors.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Estimate intrinsic vs extrinsic cancer risk.
- How was the study done?
Modelling with several approaches.
- How many people, animals or samples were studied?
Not applicable.
- What was actually found?
Extrinsic factors dominate.
- How large was the observed effect?
Intrinsic <10-30%.
- What do the results mean in everyday life?
Much cancer is preventable.
- What are the study's limitations?
Model-based; contested.
- What does it say about Elawady's specific claim?
Contradicts 'not caused by external agents'.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Which specific exposures.
Scientific in-depth review
1. Full reference
- Authors
- Wu S et al.
- Journal
- Nature
- Year
- 2016
- Identifier
- PMID 26675728 DOI 10.1038/nature16166
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
No competing financial interests; NIH grants (PubMed record)
2. Research question
How much of lifetime cancer risk is due to intrinsic (unavoidable) vs extrinsic factors?
3. Study design and population
- Study design
- Other – Modelling and epidemiological analysis (four complementary approaches)
- Population
Tissue-specific cancer risk data
- Country
USA (authors); international data
- Period
Published 2016
- Sample size
not applicable
- Inclusion and exclusion criteria
not applicable
4. Methods and endpoints
- Exposure / intervention
Intrinsic (stem-cell division) vs extrinsic factors
- Comparator
not applicable
- Endpoints
Fraction of lifetime cancer risk
- Statistical methods
Modelling; lower-bound estimation; mutation-rate analysis
5. Actual results
- Results
Intrinsic risk factors contribute only modestly (less than about 10-30% of lifetime risk); the correlation between stem-cell divisions and cancer risk does not distinguish intrinsic from extrinsic effects; endogenous mutation rates are insufficient to explain observed cancer risks.
- Absolute risks
not applicable
- Authors' conclusion
Cancer risk is heavily influenced by extrinsic factors.
6. Strengths
- Several independent analytic approaches
- High-impact peer review
7. Weaknesses
- Model-based; contested (opposes I-CAN-117)
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Modelling assumptions.
9. Assessment of the statistical interpretation
Estimates are ranges from models.
10. Relevance to the specific claim
Directly contradicts the idea that cancer arises without external causes; counterweight to the 'bad luck' interpretation of I-CAN-117.
11. Independent contrary findings
I-CAN-117 attributes two-thirds of mutations to replication errors.
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Supports a large role of external factors in cancer.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | not applicable |
| Directness | indirect |
| 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
- Cancer is the body's own plan ('a self plan'): body cells are ordered to transform because this was necessary for the person's life; it is not caused by external agents. – Studies contradicting or limiting the claim
- Chronic disease is mostly a cumulative reaction to what enters the body daily - contaminated food, medicines and cosmetics - not a fate that comes from outside. – Studies with mixed or unclear results