Antioxidant Supplements and Breast Cancer: A Systematic Review and Meta-Analysis

Context: Breast cancer is the second most common type of cancer worldwide and the most frequent one among women. Some studies suggest a favorable role of antioxidants on breast cancer, but this is still controversial.
The main objective of this article was to determine the safety and efficacy of antioxidant supplements on breast cancer.
Data Sources: In order to gather evidence, main databases (MEDLINE, PubMed, Cochrane Library, Science Direct, Trip, Google Scholar, Institute of Scientific Information (ISI), SCOPUS, and EMBASE) as well as relevant websites were searched without time limit up to November 2016. We searched with appropriate keywords and strategies. After the quality assessment of studies, study data were extracted by 2 reviewers. Because all the outcomes were dichotomous, relative risk by using the fixed-effects model proposed by Mantel-Hanzel was used in the meta-analysis. I² values were used for the evaluation of heterogeneity. Analyses were conducted, using review manager and CMA Software.
Out of 825 studies, 652 studies were entered firstly and 14 RCTs were selected after the final review. There was not significant difference between Antioxidant and Placebo group in breast cancer incidence (P = 0.88), quality of life (P = 0.79), daily hot-flash score (P = 0.87) and toxicity such as nausea-vomiting (P = 0.87), diarrhea (P = 0.17), constipation (P = 0.35), fatigue (P = 0.14), alopecia (P = 0.22), anemia (P = 0.67), headaches (P = 0.73), leukopenia (P = 0.2), and Neutropenia (P = 0.08).
The results of our meta-analysis do not support the effectiveness of antioxidants in reducing the risk of breast cancer. Also, this study showed that there is no sufficient clinical evidence to support the effectiveness of these supplements during the treatment of patients with breast cancer. It is recommended that clinician do not emphasize on these supplements in breast cancer treatment.