19 December 2019
A study recently published in the Journal of Clinical Oncology* found that the use of some vitamins and supplements before or during chemotherapy treatment for breast cancer was associated with increased recurrence and mortality rates.
Vitamins and supplements may interfere with or prevent the desired chemotherapy or radiation therapy effect of cell death, so it is common practice to advise patients to stop (or not to start) taking vitamins and supplements while undergoing treatment. The patients in this study were all undergoing chemotherapy for breast cancer, using the same medications, but with different dosing schedules. The treatment regimen was doxorubicin (also known as Adriamycin), cyclophosphamide and paclitaxel, commonly referred to as AC-T. Patients were surveyed on vitamin and supplement use prior to starting chemotherapy and after treatment. Median follow up was 8.1 years.
There were 1134 patients included in this study. 251 experienced a recurrence and 181 died – these patients were more likely to be older, Black, post-menopausal, have a higher body mass index, and have poorer tumor prognostic factors including 4 or more positive lymph nodes, and estrogen / progesterone receptor or Her2/neu negative tumors. 17.5% reported use of any antioxidant (vitamin A, vitamin C, Vitamin E, carotenoids, and co-enzyme Q12) during chemotherapy treatment and 44% used multivitamins.
The findings included:
- Use of antioxidant supplements both before and during chemotherapy was associated with an increased risk of cancer recurrence and death, but the numbers were not statistically significant
- The researchers were not able to determine if there was any specific relationship between the use of individual antioxidant supplements and risks of recurrence or death. There was a relationship with vitamin A but analysis for this supplement only included 5 patients
- There were no relationships between use of antioxidants only before or only during treatment and outcomes
- Vitamin B12 use both before and during chemotherapy was associated with increased risk of recurrence and death
- Iron use during chemotherapy was associated with higher recurrence risks as was use both before and during treatment
- Omega 3 use both before and during treatment was associated with increased recurrence risk but not death
- There did not appear to be any association between recurrence or survival and the use of multivitamins, vitamin D, glucosamine, melatonin, acidophilus, folic acid, or vitamin B6
One of the authors’ conclusions was that “we found some support for the notion that use of dietary supplements during chemotherapy could have a negative impact on recurrence and overall survival.” It is important to stress that this was an observational study, which means direct cause and effect cannot be determined. Relative, not absolute risks, were reported. In addition, the number or women who reported taking non-multivitamin supplements was just under 200. While news reports noted that supplements were associated with a 40% increased risk of recurrence a weaker association with death, these numbers did not meet statistical significance. The authors noted that “a review… in 2010 concluded that insufficient evidence existed with regard to safety of dietary supplements to make recommendations, and that may still be the case.”
Despite the limitations of this study and the inability to draw firm conclusions, it is still recommended that patients who receive a recommendation for chemotherapy or radiation therapy inform their medical team of all vitamins and supplements that they are taking, and it still is considered best practice to avoid antioxidant supplements while undergoing treatment.
*If you are not able to access the full study and would like a copy, please email me: contact at drattai dot com