Antioxidant supplements are associated with increased disease recurrence and statistically nonsignificant increased risk of mortality in patients with breast cancer who were receiving cyclophosphamide, doxorubicin, and paclitaxel, according to findings from a study reported in the Journal of Clinical Oncology.
As part of the observational DELCap (diet, exercise, lifestyle, and cancer prognosis) study, researchers evaluated 1,134 patients’ self-reported use of dietary supplements before and during their cancer treatment. They measured recurrence and survival at six months after study enrollment.
The researchers found that any antioxidant use (e.g., vitamins A, C, and E; carotenoids; coenzyme Q10) before and during chemotherapy treatment was associated with an increased risk of recurrence and death. Use of vitamin B12 supplements before and during treatment was significantly associated with poorer disease-free and overall survival, and use of iron supplements before and during treatment was significantly associated with recurrence. However, use of a multivitamin did not have an effect on treatment outcomes.
The authors said that their findings support “recommendations for caution among patients when considering the use of supplements, other than a multivitamin, during chemotherapy.”