Breast cancer: dietary supplements during chemo are tied to worse survival

  • Ambrosone CB & al.
  • J Clin Oncol
  • 19 Dec 2019

  • curated by Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • 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.

Study design

  • 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.

Key results

  • 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).

Limitations

  • Short trial (6 months).
  • Observational design.