Meta-analysisindependent cross-checkabstract only checked★ key study I-CHM-06 in-depth review
With modern techniques, radiotherapy's heart and lung risks are small for non-smokers
Estimating the Risks of Breast Cancer Radiotherapy: Evidence From Modern Radiation Doses to the Lungs and Heart and From Previous Randomized Trials.
Overview
Taylor C et al.. J Clin Oncol 2017 · PMID 28319436 · DOI 10.1200/JCO.2016.72.0722
About 0.3% risk of radiation-related heart death or lung cancer in non-smokers, higher in smokers.
Does the study support the specific claim? Partly · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Estimate absolute RT risks.
- How was the study done?
Dose review + IPD meta-analysis.
- How many people, animals or samples were studied?
40,781 women.
- What was actually found?
Small absolute risks; smoking key.
- How large was the observed effect?
Cardiac mortality RR 1.30.
- What do the results mean in everyday life?
Stop smoking before/after radiotherapy.
- What are the study's limitations?
Smoking modelled.
- What does it say about Elawady's specific claim?
Puts Darby in perspective.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Individual dose-specific risk.
Scientific in-depth review
1. Full reference
- Authors
- Taylor C et al.
- Journal
- J Clin Oncol
- Year
- 2017
- Identifier
- PMID 28319436 DOI 10.1200/JCO.2016.72.0722
- Verification
- verified – PubMed esummary + efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Absolute long-term risks of modern breast radiotherapy.
3. Study design and population
- Study design
- Meta-analysis – Systematic review of modern doses plus IPD meta-analysis of 75 RCTs
- Population
Women randomised to RT vs no RT
- Country
International
- Period
Doses 2010-2015
- Sample size
40,781 women in 75 trials; 647 regimens
- Inclusion and exclusion criteria
RCTs of RT vs none; published modern dose data
4. Methods and endpoints
- Exposure / intervention
Radiotherapy (modern doses: lung 5.7 Gy, heart 4.4 Gy)
- Comparator
No radiotherapy
- Endpoints
Lung cancer, cardiac mortality
- Statistical methods
Rate ratios; excess RR per Gy; application to smoker/non-smoker rates
5. Actual results
- Results
Lung cancer >=10 y RR 2.10 (1.48-2.98); 0.11 ERR/Gy. Cardiac mortality RR 1.30 (1.15-1.46); 0.04 ERR/Gy. Absolute modern-RT risks: lung cancer ~4% in long-term smokers vs 0.3% non-smokers; cardiac mortality ~1% smokers vs 0.3% non-smokers.
- Absolute risks
Cardiac mortality ~0.3% (non-smokers) and ~1% (smokers); lung cancer ~0.3% vs ~4%
- Authors' conclusion
For most non-smokers the benefits far outweigh the risks; for long-term smokers risks may outweigh benefits; stopping smoking reduces RT risk.
6. Strengths
- Randomised evidence
- Modern doses
- Absolute risks
7. Weaknesses
- Smoking status unavailable in trials (modelled)
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
IPD meta-analysis; modelling assumptions.
9. Assessment of the statistical interpretation
Converts relative per-Gy risks into absolute risks; shows smoking as main modifier.
10. Relevance to the specific claim
Absolute-risk context for Darby; shows smoking matters (contradicts dismissal of smoking).
11. Independent contrary findings
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Key study for net benefit of radiotherapy.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- After breast-cancer radiotherapy, the rate of major coronary events rises by 7.4% for every Gray of mean radiation dose to the heart, linearly and without threshold (Darby 2013). – Studies contradicting or limiting the claim
- Anthracycline chemotherapy (and chest radiotherapy) can cause chronic, dose-dependent heart damage that may appear or progress years after treatment. – Studies supporting the claim
- Chemotherapy and radiotherapy can cause second cancers (e.g., breast cancer after chest radiation for Hodgkin disease, therapy-related myeloid leukaemia) years after cure. – Studies with mixed or unclear results
- Smoking (and similar exposures) should not be blamed for cancer; only massive exposures such as Hiroshima cause cancer, and there is 'no such thing as early death' from smoking. – Studies contradicting or limiting the claim