[ RadSafe ] Antioxidants may not be beneficial in RT

[alstonchris at netscape.net]

John

It makes some intuitive sense, don't you think?  I.e., since 70% of the tumoricidal effects of most RT is secondary to free radical production, the antioxidants may be protecting the tumors, as well as normal tissues.  I suppose that such a protective action could be enhanced, if the tumor were hypoxic, no?

Awaiting the slings and arrows, I am,
cja

John Jacobus <crispy_bird at yahoo.com> wrote:
>Another example of the complexities of biology.
>
>-------------------
>Antioxidant supplements show mixed effects on
>radiation therapy
>9/21/2005
>By: Reuters Health
>
>NEW YORK (Reuters Health), Sep 21 - Antioxidant
>vitamins may reduce the severity of adverse effects of
>radiation therapy but may increase the risk of
>recurrence of the underlying tumor, according to a
>report by Canadian researchers.
>
>Although many patients take vitamin and mineral
>supplements in the hope of improving cancer treatment
>outcomes, the authors point out, few studies have
>examined the efficacy and safety of adjuvant
>antioxidant vitamin supplementation in this setting. 
>
>Dr. Isabelle Bairati from Laval University Cancer
>Research Center, Quebec City, and colleagues examined
>whether daily supplementation with alpha-tocopherol
>and beta-carotene could reduce the rate and severity
>of acute adverse effects of radiation therapy in 540
>patients with head and neck cancer. 
>
>Severe acute adverse effects during radiation therapy
>occurred in fewer patients in the supplement group
>(19.2%) than in the control group (24.8%), the authors
>report in the August 20th issue of the Journal of
>Clinical Oncology.
>
>There was a tendency for less severe adverse effects
>during radiation therapy at any site and overall among
>those receiving antioxidants, the results indicate.
>Combined treatment with alpha-tocopherol and
>beta-carotene was associated with a significant 62%
>reduction in adverse effects overall and a similar
>reduction among patients with cancer of the larynx. 
>
>However, local recurrence of tumor was 37% more likely
>among patients in the supplementation group, the
>investigators report, and was somewhat higher among
>patients treated with both antioxidants. 
>
>In light of these findings, the researchers observe
>that "randomized controlled trials should be conducted
>to provide clear scientific evidence regarding the
>efficacy and safety of antioxidant use as adjuvant
>therapies for cancer."
>
>In an accompanying editorial, Dr. Kevin Camphausen and
>associates from the National Cancer Institute in
>Bethesda, MD, agree, pointing out that "the issue of
>patient self-supplementation with antioxidants during
>radiotherapy must also be addressed in more detail
>given the results of this study."
>
>"Without any definitive data on this issue," they
>conclude, " a reasonable approach would be to avoid
>unnecessary supplementation during and after
>radiotherapy."
>
>J Clin Oncol 2005;23:5805-5813,5455-5457.

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