Warning: Breast Cancer Patients Undergoing Chemotherapy Should Avoid Consuming Any Antioxidants Or Health Supplements
Source: Thailand Medical News Dec 21, 2019 4 years, 11 months, 2 days, 5 hours, 30 minutes ago
Patients suffering from
breast cancer who take the
dietary supplements known as antioxidants, as well as iron, vitamin B12, and omega-3 fatty acids, during
chemotherapy may be at increased risk of disease recurrence and death, according to new study results appearing in the
Journal of Clinical Oncology.
Researchers from the SWOG
Cancer Research Network, a cancer clinical trials network funded by the National Cancer Institute (NCI) through the National Institutes of Health, have conducted a study that confirms previous medical guidance advising cautious use of any
supplements, other than a multivitamin, for
cancer patients undergoing
chemotherapy.
A growing body of research in the last 20 years shows that, despite their
cancer-fighting reputation, antioxidants such as vitamin E, beta-carotene, and selenium can actually increase risk of some
cancers, cause some
cancers to return after treatment, or interfere with the effects of
chemotherapy. As part of the nation's oldest and largest publicly-funded
cancer research network, SWOG has conducted some of this work. Its landmark Selenium and Vitamin E Cancer Prevention Trial (SELECT) showed that vitamin E
supplementation increases the risk of prostate
cancer in healthy men.
The new study, led by Dr Christine B. Ambrosone, Ph.D., of Roswell Park Comprehensive Cancer Center, is the first investigation of the effects of
supplement use during
breast cancer treatment, and only the second to investigate the effects of supplement use during any kind of
cancer treatment. The first was conducted by Charles Fuchs, MD, MPH, the director of Yale
Cancer Center, who found that vitamin C may be helpful for people undergoing chemotherapy treatment for colorectal
cancer.
Dr Ambrosone, chair of the Department of Cancer Prevention and Control at Roswell Park told
Thailand Medical News, "Although this is an observational study and the number of users of supplements was fairly small, the results are compelling. Patients using any
antioxidant before and during chemotherapy had an increased risk of their
breast cancer returning and, to a lesser degree, had an increased risk of death. Vitamin B12, iron, and omega-3 fatty acid use was also associated with poorer outcomes."
Dr Ambrosone conducted her study as part of S0221, a randomized phase III SWOG trial determining the best dose and schedule for using three chemotherapy drugs: doxorubicin, cyclophosphamide, and paclitaxel as adjuvant therapy for high-risk, early-stage
breast cancer. In its first iteration, the trial enrolled 2,716 patients between 2003 and 2010. Patients were followed f
or a median of six years to identify any side effects from the
chemotherapy combinations tested and to measure how long, if ever, it took for their
breast cancer to return.
The question as to whether vitamin and mineral
supplements, in particular the type known as
antioxidants, help or hurt
cancer patients is a matter of debate and dueling research findings. Some evidence suggests that antioxidants can interfere with the cancer-killing effects of
chemotherapy. That's because these chemical treatments cause oxidative stress, a chemically-triggered reaction in the body, which in turn kills
cancer cells. But
antioxidants fight oxidative stress, which means they can blunt the effects of
chemotherapy. At the same time, a few studies, such as Fuchs,' show benefits to
cancer patients who take dietary
supplements.
To study the role
supplements might play in
chemotherapy response, Dr Ambrosone and her team asked every woman and man randomized onto S0221 whether they would answer detailed questionnaires about their use of dietary
supplements, first at the time they were assigned to a treatment group, then again six months after their
chemotherapy was complete. Of the 2,014 patients eligible for this part of the study, 1,607 or 80 percent agreed.
In the end, 1,134 patients completed both surveys, and of these, 18 percent used at least one
antioxidant daily, while 44 percent took multivitamins. Here's what researchers found:
-Patients who reported taking any
antioxidant ie vitamins A, C, E and carotenoids and Coenyzme Q10, were 41 percent more likely to have their
breast cancer return when they took the
supplements both before and during
chemotherapy treatment
-Patients had a similar, but weaker, increased risk of death when taking those
antioxidants
-Patients taking vitamin B12, iron, and omega-3 fatty acid
supplements were at significantly greater risk of
breast cancer recurrence and death
-Patients taking multivitamins showed no signs of poorer or better outcomes after
chemotherapy
Dr Ambrosone cautions that her study results are not definitive enough to influence how doctors treat
cancer patients. To do that, she notes, the research community would need to run a larger, randomized trial testing groups who do and do not take
supplements to get a clear and strong connection. However, she said the results do support the current cautious approach to
supplement use for people undergoing
chemotherapy.
Dr Ambrosone added, "People diagnosed with any
cancer should talk with their doctors about whether they should be taking vitamins or other
supplements. 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."
Dr Ambrosone advises that if changes in taste or loss of appetite related to the effects of
cancer treatment are making whole vegetables, fruits, and grains unappealing or difficult to eat, patients should seek out guidance from their medical team or a dietician to find out ways to incorporate these foods into their diets.
Reference: Dietary Supplement Use During Chemotherapy and Survival Outcomes of Patients With Breast Cancer Enrolled in a Cooperative Group Clinical Trial (SWOG S0221), Christine B. Ambrosone, Gary R. Zirpoli, Alan D. Hutson, William E. McCann, Susan E. McCann, William E. Barlow, Kara M. Kelly, Rikki Cannioto, Lara E. Sucheston-Campbell, Dawn L. Hershman, Joseph M. Unger, Halle C.F. Moore, James A. Stewart, Claudine Isaacs, Timothy J. Hobday, Muhammad Salim, Gabriel N. Hortobagyi, Julie R. Gralow, George T. Budd, and Kathy S. AlbainJournal of Clinical Oncology 0 0:0
https://ascopubs.org/doi/abs/10.1200/JCO.19.01203 
