Antioxidant pills may benefit chemotherapy patients

From USA Weekend, July 1, 2007-07-02
There is some controversy over whether patients on chemotherapy
should take anti-oxidants. The main concern: Do supplements like
vitamins E and C, beta carotene and selenium counteract cancer
treatment?
A new review of 1500 patients found that taking antioxidant
supplements with chemotherapy actually might increase survival rates,
tumor shrinkage and the patient's ability to tolerate chemotherapy.
Discouraging antioxidants is not scientifically valid, suggests the
study [below], which was co-authored by Robert Newman, Ph.D., of M.D.
Anderson Cancer Center and Keith Block, M.D., medic al and scientific
director of the Block Center for Integrative Cancer Cure.
4/25/2007 - Antioxidants supplements may help increase cancer
survival rates, tumour response, and the patient's ability to tolerate
chemotherapy, concludes a new review.
The review could reignite the debate about potential benefits or
risks, with some studies reporting that the supplements may have a
detrimental effect.
"This review demonstrates that there is no scientific support for
the blanket objection to using antioxidants during chemotherapy. In
addition, it also appears that these supplements may help mitigate the
side effects of chemotherapy," said lead author Keith Block, from the
Institute for Integrative Cancer Research and Education and the
University of Illinois.
Antioxidants, such as vitamins A, C and E and carotenoids like
beta-carotene, are believed to exert a protective effect on cells. They
scavenge toxic molecules called free-radicals, which cause oxidative
stress and can lead to DNA cell damage.
"Much debate has arisen about whether antioxidant supplementation
alters the efficacy of cancer chemotherapy," wrote Block in Cancer
Treatment Reviews. "Some have argued that antioxidants scavenge the
reactive oxygen species integral to the activity of certain
chemotherapy drugs, thereby diminishing treatment efficacy. Others
suggest antioxidants may mitigate toxicity and thus allow for
uninterrupted treatment schedules and a reduced need for lowering
chemotherapy doses."
The researchers searched databases and identified 19 trials (1,554
participants) that met all evaluation criteria, including the use of
randomized trials with a control group, and the reporting of treatment
response (tumour shrinkage) and survival data.
Block and his co-authors report that survival data showed similar
or better survival rates for the antioxidant group than the control
group, with none of the trials supporting the theory that antioxidant
supplements diminish the effectiveness of chemotherapy.
Additionally, 15 of 17 trials that assessed chemotherapy
toxicities, including diarrhoea, weight loss, nerve damage and low
blood counts, concluded that the antioxidant group suffered similar or
lower rates of these side effects than the control group.
The authors noted that reducing side effects may help patients
avoid having to cut back on their chemotherapy dosing, interrupt
scheduled treatments, or abandon treatment altogether. This in turn, is
likely to favourably impact treatment outcomes.
"This study, along with the evolving understanding of
antioxidant-chemotherapy interactions, suggests that the previously
held beliefs about interference do not pertain to clinical treatment,"
said co-author Robert Newman from M.D. Anderson Cancer Center.
"The lack of negative impact of antioxidant supplementation on
efficacy of ROS-generating chemotherapy in the studies reviewed, and
the potential to diminish dose-limiting toxicity suggest that the
clinical application of antioxidant supplementation during chemotherapy
should be further explored," concluded the researchers.
"Future research on concurrent use of antioxidants and chemotherapy
should employ larger sample sizes and better research designs."
Source: Cancer Treatment Reviews (Elsevier)
May 2007, doi: 10.1016/j.ctrv.2007.01.005
"Impact of antioxidant supplementation on chemotherapeutic efficacy: A
systematic review of the evidence from randomized controlled trials"
Authors: K.I. Block, A.C. Koch, M.N. Mead, P.K. Tothy, R.A. Newman and C. Gyllenhaal