Rad Exposure during middle age

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Ivona
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Rad Exposure during middle age

Postby Ivona » Tue Oct 26, 2010 10:26 am

> Risk of cancer due to radiation exposure in middle age may be higher than
> previously estimated
> October 25th, 2010 in Medicine & Health / Cancer
>
>
> Contrary to common assumptions, the risk of cancer associated with radiation
> exposure in middle age may not be lower than the risk associated with exposure
> at younger ages, according to a study published online October 25 in the Journal
>
> of the National Cancer Institute.
> It is well known that children are more sensitive than adults to the effects of
> radiation and that they have a greater risk of developing radiation-induced
> cancer than adults. Some data also suggest that, in general, the older a person
> is when exposed to radiation, the lower their risk of developing a
> radiation-induced cancer. On the other hand, statistical evidence from long-term
>
> studies of atomic bomb survivors in Japan indicates that for radiation exposure
> after about age 30, the risk of developing radiation-induced cancer does not
> continue to decline.
> To explore this issue, David J. Brenner, Ph.D., D.Sc., at Columbia University in
>
> New York, and colleagues reanalyzed the Japanese atomic bomb survivor data
> assuming two different pathways through which radiation exposure can ultimately
> lead to cancer. The first is initiation of gene mutations that convert normal
> stem cells to premalignant cells that could eventually lead to cancer. The
> second is radiation induced promotion, or expansion, of the number of existing
> premalignant cells in the body. The initiation effect is more likely to play a
> role in children than in adults, they reason, because cells initiated at an
> early age have a longer time available to expand in number and progress on the
> pathway to cancer. The promotion effect, on the other hand, is more likely to be
>
> important for radiation exposures in middle age, because the adult body already
> contains larger numbers of premalignant cells.
> The researchers developed a model based on these biological effects and applied
> the model to the Japanese atomic bomb survivor data. They found that the model
> was able to reproduce the cancer risk patterns associated with age at radiation
> exposure observed in these survivors. They then applied the same model to
> predict cancer risks as a function of age in the U.S. population and found that
> the cancer risks predicted by the model were consistent with the data in the age
>
> range from about 30 to 60.
> The authors conclude that cancer risk after exposure in middle age may increase
> for some tumor types contrary to conventional wisdom. They add that these
> findings could have practical implications regarding x-ray diagnostic tests,
> which are predominantly performed on middle aged adults, as well as for
> occupations that involve radiation exposures, again where most exposures are in
> middle age.
> "Overall, the weight of the epidemiological evidence suggests that for adult
> exposures, radiation risks do not generally decrease with increasing age at
> exposure," they write, "and the mechanistic underpinning described here provides
>
> this conclusion with some biological plausibility."
> In an accompanying editorial, John D. Boice, Sc.D., of the International
> Epidemiology Institute, Rockville, Md., and Vanderbilt University, Nashville,
> notes that there are uncertainties in generalizing the Japanese data to a U.S.
> population. He also notes that other data and other models contradict the
> results of this study. However, he concludes that this biology-based model
> "raises provocative hypotheses and conclusions that, although preliminary, draw
> attention to the continued importance of low-dose radiation exposures in our
> society."
> Provided by Journal of the National Cancer Institute
> "Risk of cancer due to radiation exposure in middle age may be higher than
> previously estimated." October 25th, 2010.
> http://www.physorg.com/news/2010-10-can ... e-age.html
>
>
>
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dx'd Oct '08 (age 48)
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