The impact of antioxidant supplements on the risk of recurrence, mortality, inflammatory markers, and patient-reported outcomes in women with breast cancer: A systematic review

<b>Abstract</b> <b>Purpose:</b> Many breast cancer (BC) patients take antioxidant supplements during cancer therapy to improve health outcomes, but little is known about their benefits. This systematic review aimed to summarise preliminary findings and determine the impact of antioxidants on clinical and patient-reported outcomes (PROs) among BC patients receiving cancer treatments. <b>Methods:</b> A search of English-language articles from 2010 onwards was conducted in PubMed, Web of Science, EMBASE and Cochrane Library. Observational and interventional studies were considered for inclusion. Antioxidant supplements were defined as oral, serum and intravenous antioxidants, with dietary antioxidants excluded. <b>Results:</b> Eight eligible studies were identified. Four studies examined disease recurrence and mortality, one reported inflammation levels, two evaluated PROs (fatigue, depression, quality of life [QoL], lymphoedema), and one reported both inflammation levels and cognitive function. Antioxidant use was significantly associated with a decreased risk of recurrence (HR: 0.78, 95% CI: 0.63-0.95; vitamin C: HR: 0.73, 95% CI: 0.55‐0.97, vitamin E: HR: 0.71, 95% CI: 0.54‐0.94) and mortality (HR: 0.82, 95% CI: 0.65-1.02; HR: 0.76, 95% CI: 0.58‐1.00) in two of the four studies. Findings on reduced inflammation and lymphoedema were significant (p&lt;0.05), but fatigue, depression and QoL were insignificant. Additionally, antioxidant supplements may have cognitive benefits. <b>Conclusions:</b> Antioxidant supplements used by these patients may decrease recurrence and mortality, inflammation and lymphoedema volume, and improve cognitive health. However, inconsistent results warrant further investigation. Adequately powered studies, with specific timings and dosages of antioxidants, will be highly beneficial to address ongoing concerns regarding antioxidant use in managing BC.