- Use of dietary supplements, such as vitamins A, C, and E, before and during chemotherapy was associated with poorer DFS and OS in a cohort study of patients with breast cancer enrolled in SWOG S0221.
Why this matters
- Findings provide empirical support for recommendations cautioning against antioxidant use during chemotherapy because of concerns that 1 cytotoxic mechanism might involve reactive oxygen species generation.
- Prospective cohort of patients randomly assigned to chemotherapy with doxorubicin, cyclophosphamide, and paclitaxel as part of a clinical trial.
- Patients were questioned about dietary supplement use before and during treatment (n=1134).
- Primary outcomes: DFS and OS.
- Funding: NIH; Breast Cancer Research Foundation; others.
- With adjustment for age, tumor characteristics, alcohol consumption, among others, any antioxidant supplement use (vitamins A, C, and E; carotenoids, coenzyme Q10) before and during chemotherapy was nonsignificantly associated with (adjusted [a]HRs):
- Worse DFS: 1.41 (P=.06); and
- Worse OS: 1.40 (95% CI, 0.90-2.18).
- Nonantioxidant vitamin B12 use before and during chemotherapy was associated with (aHRs; 95% CIs):
- Worse DFS: 1.83 (1.15-2.92); and
- Worse OS: 2.04 (1.22-3.40).
- Iron use before and during chemotherapy was associated with worse DFS:
- aHR, 1.91 (95% CI, 0.98-3.70).
- Short trial (6 months).
- Observational design.