Breast cancer patients who use certain supplements before and during chemotherapy are more likely to experience disease recurrence and related death than those who do not use supplements, according to data from more than 1,100 patients.
Lead researcher Christine Ambrosone, PhD, the chair of the Department of Cancer Prevention and Control at Roswell Park Comprehensive Cancer Center, in Buffalo, N.Y., said the findings should provide a clear message to patients and physicians. “I’d recommend that [cancer patients] try to get their vitamins and minerals, including antioxidants, from food,” she said in a press release about the study.
According to Dr. Ambrosone, research indicates that supplements—particularly antioxidants such as vitamin E, beta carotene and selenium, which some patients see as cancer fighting—can interfere with the efficacy of chemotherapy and increase the risk for some cancers or cause recurrences.
To add to the understanding of this topic, she and her colleagues asked 1,134 patients with breast cancer who were undergoing treatment about their use of supplements. The patients were part of a randomized trial examining a variety of treatment regimens with cyclophosphamide, doxorubicin and paclitaxel as adjuvant therapy for early-stage, high-risk breast cancer. The researchers surveyed patients about their supplement use at the start of chemotherapy and six months later, following them for up to 12 years after treatment began.
According to the results, which were published in the Journal of Clinical Oncology (2020;38:804-814), roughly 17% of patients said they were taking an antioxidant and 44% were taking a multivitamin during treatment. After controlling for clinical and lifestyle factors, vitamin B12 use both before and during chemotherapy was associated with a significantly higher likelihood of recurrence (adjusted hazard ratio [aHR], 1.83; 95% CI, 1.15-2.92; P=0.01) and death (aHR, 2.04; 95% CI, 1.22-3.40; P=0.01). In addition, iron use during chemotherapy was associated with a significantly higher risk for recurrence (aHR, 1.79; 95% CI, 1.20-2.67; P=0.01). The researchers found no association between multivitamin use and survival outcomes.
Use of any antioxidant supplements, specifically vitamins A, C and E; carotenoids; and coenzyme Q10 before and during treatment was associated with a trend for increased risk for breast cancer recurrence, although this association was not statistically significant (aHR, 1.41; 95% CI, 0.98-2.04; P=0.06). There was a similar trend toward a higher risk for death during the follow-up period among antioxidant users (aHR, 1.40; 95% CI, 0.90-2.18; P=0.14).
Although Dr. Ambrosone and her co-investigators noted that the lack of statistical significance they found with antioxidant use could have been due to the limited number of antioxidant users and the small numbers of cancer recurrences and death, they wrote, “Nonetheless, these findings of increased poor outcomes with use of antioxidant supplements are congruent with concerns that use of antioxidants during chemotherapy could reduce [its] cytotoxic effects.”
The investigators concluded that these “associations between survival outcomes and use of antioxidant and other dietary supplements both before and during chemotherapy” support existing “recommendations for caution among patients when considering the use of supplements, other than a multivitamin, during chemotherapy.”
Barbara Jacoby is an award winning blogger that has contributed her writings to multiple online publications that have touched readers worldwide.