Dietary Supplement Use During Adjuvant Chemotherapy and Treatment Outcomes in Patients With Early Breast Cancer

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As reported in the Journal of Clinical Oncology by Ambrosone et al, an analysis of the SWOG S0221 trial population suggests that use of antioxidant and nonantioxidant dietary supplements, but not multivitamins, before and during adjuvant chemotherapy may be associated with poorer treatment outcomes in patients with high-risk early breast cancer.

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Study Details

The phase III SWOG S0221 trial evaluated the optimal dose and schedule of anthracycline-taxane adjuvant chemotherapy in women with high-risk early breast cancer. The current analysis involved 1,134 (of 2,014) patients enrolled in SWOG S0221 who answered baseline and follow-up questionnaires that included items on dietary supplement use. Analysis of associations of dietary supplement use and clinical outcomes were adjusted for clinical and lifestyle factors.

Key Findings

Use of any antioxidant supplement (vitamins A, C, and E; carotenoids; or coenzyme Q10) both before and during adjuvant treatment was associated with a borderline increased risk of recurrence vs no such use (adjusted hazard ratio [aHR] = 1.41, 95% confidence interval [CI] = 0.98–2.04, P = .06). Such use was associated with a nonsignificant increase risk of overall mortality (aHR = 1.40, 95% CI = 0.90–2.18, P = .14). As noted by the investigators, weaker associations of outcomes with individual antioxidants were observed that may have reflected use among smaller numbers of patients. No significant associations with outcomes were observed for antioxidant use only before treatment or only during treatment.


  • There was some evidence of an association with antioxidant and nonantioxidant supplement use and risk of poorer outcomes.
  • No increased risk was associated with multivitamin use.

With regard to nonantioxidant supplements, use of vitamin B12 both before and during chemotherapy was significantly associated with poorer disease-free survival (aHR = 1.83, P < .01) and overall survival (aHR = 2.04, P < .01) and use of iron during chemotherapy was associated with greater risk of recurrence (aHR = 1.79, P < .01).

Neither multivitamin use nor vitamin D use was associated with survival outcomes.

The investigators concluded, “Associations between survival outcomes and use of antioxidant and other dietary supplements both before and during chemotherapy are consistent with recommendations for caution among patients when considering the use of supplements other than a multivitamin during chemotherapy.”

Christine B. Ambrosone, PhD, of Roswell Park Comprehensive Cancer Center, is the corresponding author for the Journal of Clinical Oncology article.

Disclosure: The study was supported by the Breast Cancer Research Foundation, a Roswell Park Comprehensive Cancer Center Cancer Center support grant, and the National Cancer Institute. For full disclosures of the study authors, visit

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.