Use of Antioxidants During Chemotherapy May Increase Risk for Breast Cancer Recurrence

Use of antioxidant supplements during chemotherapy treatment increased the risk for breast cancer to recur by 41%, according to study results published in the Journal of Clinical Oncology.

Therefore, researchers from Roswell Park Comprehensive Cancer Center urged patients with breast cancer being treated with chemotherapy to consult with their physicians first before taking vitamins.

“People diagnosed with any cancer should talk with their doctors about whether they should be taking vitamins or other supplements,” lead study author Dr. Christine B. Ambrosone, said in a press release. “I’d recommend that they try to get their vitamins and minerals — including antioxidants — from food. With a healthy and balanced diet, you can get all the nutrients your body needs, even while undergoing chemo.”

One cytotoxic mechanism of cancer therapeutics is through the generation of reactive oxygen species — a type of unstable molecule that contains oxygen and that easily reacts with other molecules in a cell, like peroxides. Because of this, the researchers noted that there has been concern that use of dietary supplements during treatment, particularly antioxidants, could reduce treatment efficacy. However, supplements could also help to reduce side effects from treatment without impacting efficacy.

The Diet, Exercise, Lifestyle and Cancer Prognosis (DELCaP) study was correlated to another phase 3 trial evaluating patients with breast cancer who received different treatment schedules with chemotherapy. With this, the researchers queried 1,134 patients on their use of supplements at randomization and at completion of chemotherapy.

A baseline questionnaire was sent before patients began chemotherapy, asking about regular use (at least once per week) of supplement use before diagnosis and between diagnosis and enrollment in the trial. If surveys were not returned within two weeks, each patient was called with a reminder and an offer to complete the questionnaire over the telephone, followed by monthly calls if there was no response. Approximately six months after treatment randomization, a second questionnaire was sent to patients who had completed the first questionnaire, asking about supplement use during chemotherapy.

The researchers previously reported that antioxidant use had no effect on reducing chemotherapy-induced peripheral neuropathy; however, multivitamins did.

“These associations, however, must be balanced against potential adverse effects of supplement use on recurrence and mortality,” they explained. “Here, we address the primary goal of the DELCaP study: To determine whether use of supplements during chemotherapy, particularly antioxidants, has any effects on survival outcomes.”

They found that there were indications that use of any antioxidant supplement — like vitamins A, C, and E; carotenoids; and coenzyme Q10 – both before and during treatment was associated with an increased risk of recurrence and, to a lesser extent, death.

Compared with non-antioxidants, vitamin B12 use both before and during chemotherapy was also significantly associated with poorer disease-free survival overall survival. Moreover, the use of iron during chemotherapy was significantly associated with recurrence, as used both before and during treatment.

Multivitamin use was not associated with survival outcomes.

“Our findings from this prospective study in the context of a cooperative group clinical trial indicate that use of antioxidant supplements during chemotherapy, as well as iron and vitamin B12, may increase the risk of breast cancer recurrence and mortality,” the researchers concluded. “Short of a randomized trial of supplements in patients with cancer, the findings provide some empirical data for consideration when discussing with patients the use of dietary supplements during chemotherapy.”