New research raises concerns about the use of certain vitamin supplements during chemotherapy treatment for breast cancer, indicating that users may experience a greater risk of the cancer recurring or death.
In findings published last month in the Journal of Clinical Oncology, researchers evaluated data on more than 1,100 patients with breast cancer who were randomly assigned to a trial of chemotherapy including cyclophosphamide, doxorubicin, and paclitaxel. They were questioned on their use of supplements before and during treatment, and followed for six years to calculate the rates of cancer recurrence and survival.
Use of any antioxidant supplement, including vitamins A, C, and E, carotenoids, and coenzyme Q10, was linked to an increased risk of cancer recurrence. Patients who took these antioxidants were 41% more likely to have cancer recurrence when taking the supplements before and during chemo. Patients who took antioxidant supplements were also 40% more likely to die during follow-up, compared to patients who did not use them.
When considering non-antioxidant supplements, researchers focused on vitamin B-12, iron, omega-3, and multivitamins. According to their findings, using B12 before and during chemo increased cancer recurrence by 83% and increased the risk of death by 22%.
Women taking omega-3 supplements before and during chemo had a 67% increased risk of cancer recurrence, while those taking iron supplements had a 79% higher likelihood of experiencing a cancer recurrence.
However, using multivitamins during chemotherapy was not linked to increased risk of death or cancer recurrence.
The findings from this study are consistent with prior doctor recommendations, which encourage women with breast cancer to exercise caution when using antioxidants and other vitamin supplements.
Researchers speculate antioxidants may interfere with the ability of chemotherapy to kill cancer cells. Chemo works by generating oxidative stress on the body; antioxidants may block oxidative stress and make chemo less effective.
The number of women taking any individual supplement in the study was small, so it makes it difficult to determine the real risk to cancer patients, according to the researchers. There was also no evidence regarding supplements like Vitamin D, so more research is needed to determine which vitamins are involved and what the exact risk is.
Patients should consult their doctor regarding what supplements are safe to take before and during chemotherapy, researchers warned. However, they determined the best way to make sure you get an adequate intake of vitamins and minerals is not through supplements, but to eat a healthy, balanced diet.