MS-N162 · Dietary phytochemicals · Cancer-control observation · Stage III colon cancer · Prospective cohort within a trial · Appraised 28 October 2026
Is higher post-diagnosis intake of flavonoids or flavonoid-rich foods associated with longer disease-free or overall survival after stage III colon cancer?
Evidence at a glance
- Evidence label: No association in a large prospective observational analysis
- Benefit: None established. The highest versus lowest quintile of total flavonoid intake was not associated with disease-free survival.
- Certainty: Moderate for the reported null association, but diet was self-reported and not randomized; residual confounding and measurement error remain possible.
- Risk: The study evaluated foods, not concentrated flavonoid supplements. It cannot establish the safety of high-dose extracts or interactions with treatment.
What was studied
A prospective observational analysis included 1,625 people enrolled in CALGB/SWOG 80702 after resection of stage III colon cancer. Food-frequency questionnaires were completed within six weeks of randomization and again 14–16 months later. Total flavonoids and six subclasses were calculated. Disease-free survival was primary; overall survival was secondary. Median follow-up was 5.9 years.
What the evidence found
For the highest versus lowest quintile of total flavonoid intake, the adjusted HR for disease-free survival was 1.01 (95% CI 0.75–1.37). No flavonoid subclass was significantly associated with disease-free or overall survival, and exploratory flavonoid-rich food analyses were not significant after Bonferroni correction.
How to interpret it
Participants received standardized cancer treatment within a randomized trial, but flavonoid intake itself was observational. This negative result does not argue against eating fruits, vegetables, tea or other plant foods for general nutrition. It does argue against claiming that higher flavonoid intake has been shown to prevent colon-cancer recurrence.
Practical safety context
Food-based advice should still account for bowel function, ostomy needs, diarrhea, obstruction risk, diabetes, weight loss and treatment-specific restrictions. Concentrated extracts may have different exposures and interaction risks and were not studied here.
Questions for the care team
- Am I considering whole foods or a concentrated supplement?
- Does my bowel function or treatment require individualized fiber advice?
- What outcome am I trying to improve—nutrition, symptoms or recurrence risk?
Funding and conflicts
The analysis used the NCI-supported Alliance CALGB/SWOG 80702 platform. The accepted manuscript was available before final copyediting; detailed author conflicts should be rechecked in the final version.
Sources
Last literature search: 28 October 2026. Record appraisal: 28 October 2026. This page is educational and does not replace individualized medical advice. Symptom, biomarker or observational findings must not be interpreted as proof of tumor control, recurrence prevention or longer survival unless those outcomes were directly tested.
