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Antioxidant, Supplement Use May Worsen Breast Cancer Outcomes

Disease-free, overall survival poorer with vitamin B12 use before and during chemotherapy

THURSDAY, Dec. 26, 2019 (HealthDay News) -- Use of antioxidants and other dietary supplements before and during chemotherapy is associated with worse survival outcomes for patients with breast cancer, according to a study published online Dec. 19 in the Journal of Clinical Oncology.

Christine B. Ambrosone, Ph.D., from the Roswell Park Comprehensive Cancer Center in Buffalo, New York, and colleagues queried 1,134 patients with breast cancer randomly assigned to an intergroup metronomic trial of cyclophosphamide, doxorubicin, and paclitaxel on their use of supplements before and during treatment.

The researchers found that use of any antioxidant supplement (vitamins A, C, and E; carotenoids; coenzyme Q10) before and during treatment was associated with elevated risk of recurrence (adjusted hazard ratio [aHR], 1.41; 95 percent confidence interval [CI], 0.98 to 2.04; P = 0.06) and death (aHR, 1.40; 95 percent CI, 0.90 to 2.18: P = 0.14). Vitamin B12 use both before and during chemotherapy was associated with poorer disease-free survival (aHR, 1.83; 95 percent CI, 1.15 to 2.92; P < 0.01) and overall survival (aHR, 2.04; 95 percent CI, 1.22 to 3.40; P < 0.01). Iron use during chemotherapy was associated with recurrence (aHR, 1.79; 95 percent CI, 1.20 to 2.67; P < 0.01). There was no association seen between multivitamins and survival outcomes.

"Short of a randomized trial of supplements in patients with cancer, the findings provide some empirical data for consideration when discussing with patients the use of dietary supplements during chemotherapy," the authors write.

Several authors disclosed financial ties to the pharmaceutical industry.

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