Taking Dietary Supplements During Chemo May Increase Risk of Breast Cancer Recurrence, Death

The findings of a new study suggest that women who take dietary supplements while undergoing chemotherapy treatment for breast cancer may face an increased risk of cancer recurrence or death, particularly those who take antioxidant supplements. “Despite reported widespread use of dietary supplements during cancer treatment, few empirical data with regard to their safety or efficacy exist,” the authors of the study noted in their introduction. They found during their research that breast cancer patients who took antioxidant supplements like vitamin A, C and E before and during chemotherapy were 41% more likely to experience cancer recurrence and 40% more likely to die, compared to patients who did not use them. This study provides important information for consideration when doctors are discussing with their patients the use of dietary supplements during chemotherapy, but the researchers note that the results are not definitive enough to affect how cancer patients are treated.

Potential Adverse Effects of Dietary Supplements During Chemo

Due to continuing concerns about the potential for certain dietary supplements, particularly antioxidants, to reduce the cytotoxicity of chemotherapy treatment, the researchers set out to conduct a prospective study secondary to a therapeutic trial in order to observe the potential correlation between the use of supplements during chemotherapy and outcomes in breast cancer patients. In the study, published last month in the Journal of Clinical Oncology, the researchers analyzed data on 1,134 patients with breast cancer who were randomly assigned to a trial of cyclophosphamide, doxorubicin and paclitaxel. The patients were asked about their use of vitamin supplements before and during chemotherapy treatment and were followed for six months to evaluate cancer recurrence and survival rates. Among the study participants, 18% reported using at least one antioxidant daily, while 44% reported taking multivitamins.

According to the researchers’ findings, the use of any antioxidant supplement, such as vitamin A, vitamin C and vitamin E, carotenoids and coenzyme Q10, both before and during treatment was associated with a 41% increased risk of cancer recurrence and a 40% increased risk of death. Additionally, the use of vitamin B12 both before and during treatment was significantly associated with poorer cancer-free survival (83% increased risk of recurrence) and overall survival rates (22% increased risk of death). The use of iron during treatment, as well as both before and during treatment, was also significantly associated with disease recurrence (79%) and poorer overall survival rates among cancer patients. The researchers did not find any correlation between the use of multivitamins and breast cancer survival outcomes.

How Can Supplements Affect Chemo Treatment?

Based on their findings, the researchers recommend caution among patients who are undergoing chemotherapy for breast cancer and considering the use of antioxidants supplements, vitamin B12 or iron, due to the potential for dietary supplements to interfere with chemo. “These findings of increased risk of poor outcomes with use of antioxidant supplements are congruent with concerns that use of antioxidants during chemotherapy could reduce the cytotoxic effects of (reactive oxygen species) generated by numerous chemotherapy agents and seem to support the recommendations by some that antioxidant supplements not be consumed during cancer therapy,” the authors wrote. Chemotherapy treatment works by slowing down or stopping the growth of cancer cells and there is evidence that “antioxidants may protect tumor cells, in addition to healthy cells, from the oxidative damage intentionally caused by conventional treatments.” As a result, antioxidant supplements may render chemotherapy less effective and increase the risk of cancer recurrence as well as the risk of death among breast cancer patients.

Alternatives to Dietary Supplements During Chemo

Rather than taking vitamins or dietary supplements during chemotherapy, the study authors advise breast cancer patients try to get their vitamins and minerals through food. “With a healthy and balanced diet, you can get all the nutrients your body needs, even while undergoing chemo,” said the lead investigator for the study, Christine B. Ambrosone, PhD, of the Roswell Park Comprehensive Cancer Center in Buffalo, New York, in a press release. Ambrosone recommends that breast cancer patients who are experiencing changes in taste or appetite related to the effects of chemotherapy discuss with their doctor or dietician other ways to incorporate whole vegetables, fruits and grains into their diet.