Randomised controlled trialindependent cross-checkabstract checked★ key study I-CAN-131 in-depth review
A low-fat diet alongside breast cancer treatment may reduce relapse
Dietary fat reduction and breast cancer outcome: interim efficacy results from the Women's Intervention Nutrition Study.
Overview
Chlebowski RT et al.. J Natl Cancer Inst 2006 · PMID 17179478 · DOI 10.1093/jnci/djj494
Women who cut dietary fat while receiving standard treatment had somewhat fewer relapses (9.8% vs 12.4%), but the result was borderline.
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?
Test low-fat diet after breast cancer surgery.
- How was the study done?
Randomised trial.
- How many people, animals or samples were studied?
2,437 women.
- What was actually found?
Fewer relapses with diet (borderline).
- How large was the observed effect?
HR 0.76 (0.60-0.98).
- What do the results mean in everyday life?
Diet may help alongside treatment, not instead of it.
- What are the study's limitations?
Interim; borderline.
- What does it say about Elawady's specific claim?
Does not support diet as replacement.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
That any diet cures cancer.
Scientific in-depth review
1. Full reference
- Authors
- Chlebowski RT et al.
- Journal
- J Natl Cancer Inst
- Year
- 2006
- Identifier
- PMID 17179478 DOI 10.1093/jnci/djj494
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
NIH/NIDDK and other grants (PubMed record)
2. Research question
Does a dietary fat-reduction intervention improve relapse-free survival in women with resected early breast cancer receiving conventional management?
3. Study design and population
- Study design
- Randomised controlled trial – Randomised controlled phase III multicentre trial (WINS), interim analysis
- Population
Women with resected early-stage breast cancer receiving conventional cancer management
- Country
USA
- Period
Randomisation 1994-2001; median follow-up 60 months
- Sample size
2,437 (975 diet, 1,462 control)
- Inclusion and exclusion criteria
Resected early-stage breast cancer
4. Methods and endpoints
- Exposure / intervention
Dietary intervention to reduce fat intake (plus conventional treatment)
- Comparator
Control (conventional treatment)
- Endpoints
Relapse-free survival
- Statistical methods
Kaplan-Meier, stratified log-rank, Cox models; two-sided tests
5. Actual results
- Results
Fat intake 33.3 vs 51.3 g/day at 12 months; body weight 6 pounds lower. Relapse events 96/975 (9.8%) vs 181/1462 (12.4%); HR 0.76 (95% CI 0.60-0.98); P=.077 stratified log-rank, P=.034 adjusted Cox. Exploratory: effect may differ by hormone-receptor status.
- Absolute risks
Crude relapse 9.8% vs 12.4% (ARR 2.5 percentage points; NNT about 39 over ~5 years, recalculated)
- Authors' conclusion
A lifestyle intervention reducing dietary fat, with modest weight change, may improve relapse-free survival in patients receiving conventional cancer management.
6. Strengths
- Large randomised trial
- Hard clinical endpoint
7. Weaknesses
- Interim analysis after funding stopped
- Log-rank P not significant
- Unblinded; weight loss co-intervention
- Different diet from Tayebat
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Open-label; interim analysis; borderline significance.
9. Assessment of the statistical interpretation
HR CI log-symmetric; crude ARR 2.5 points; inconsistent significance between log-rank and Cox analyses.
10. Relevance to the specific claim
The strongest randomised 'supporting-side' evidence that diet can matter in cancer: a low-fat diet added to standard treatment may modestly reduce relapse. It concerns an adjunct to treatment and a different diet; it does not support replacing treatment.
11. Independent contrary findings
ASCO (I-CAN-105) judges evidence for diets during treatment very limited; the finding was borderline and from an interim analysis.
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Fair kernel: nutrition alongside treatment may help; no support for diet instead of treatment.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | indirect |
| Reproducibility | not replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Long-term and replicated results.
15. Linked fact checks
- Cancer will respond to the Tayebat system; a patient with a malignant tumour should start the system now (diet as cancer treatment). – Studies with mixed or unclear results