Re: Thyroid cancer?

[carol marcus <csmarcus@ucla.edu>]

At 04:04 PM 11/24/99 -0600, you wrote:
>You wrote: 
>------------------
>Does any radsefer know what are other substances (radioactive or stable)
>that could cause thyroid cancer (other than the radioactive Iodine)?
>
>Thanks,,
>
>--
>Khalid Aleissa
>e-mail: kaleissa@kacst.edu.sa
>-------------------------
>
>While I do not claim to be an expert on the subject, the EPA provided a
document
>entitled the Assessment of Thyroid Follicular Cell Tumors (EPA/630/R-97-002),
>which describes is procedures it will use to evaluate these tumors and the data
>that are needed to make these judgments.  It can be found at
>
>http://www.epa.gov/nceawww1/thyroid.htm
>
>I would rather provide a source of information rather than telling you to go
>away.  That seems to be a favorite tactic of some of subscribers lately.
>
>-- John 
>
>"Nothing great was ever achieved without enthusiasm. " 
>Ralph Waldo Emerson
>
>John Jacobus, MS
>Health Physicist
>National Institutes of Health
>Radiation Safety Branch, Building 21
>21 Wilson Drive, MSC 6780
>Bethesda, MD  20892-6780
>Phone: 301-496-5774      Fax: 301-496-3544
>jjacobus@exchange.nih.gov (W)
>jenday@ix.netcom.com (H)
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Dear Radsafers:

I have treated over 500 cases of papillary, follicular, and mixed
papillary-follicular carcinoma, and been involved with the management of
much smaller numbers of medullary thyroid carcinoma and a few Hurthle cell
carcinomas  and a few anaplastic carcinomas.  

My statement that I-131 is not a significant cause of thyroid cancer comes
from Maxon HR, Thomas SR, Saenger EL, et al.: Amer. Jour. Med. 63:967-978,
1977.  They report that the rate of I-131-induced thyroid carcinoma is 0.05
cases/yr/million person-rem for adults.  

I mentioned that autoimmune disease seems to be the most common risk for
developing thyroid cancer. In Cotran RS, Kumar V, Collins T: Robbins
Pathologica Basis of Disease, WB Saunders, 1999, p.1142 it states, "Certain
thyroid diseases such as nodular goiter and autoimmune thyroid disease
(Hashimoto thyroiditis) have been implicated as predisposing factors (35)".
Reference (35) is Gagel RF, et al.: Changing concepts in the pathogenesis
and management of thyroid carcinoma.  CA Cancer J Clin 46:261,1996.

I went to the EPA website and scanned the 51-page document, reading portions
in detail.  It is not helpful.  It is a report dealing with how EPA will use
experimental animal data on follicular carcinogenesis to set toxic chemical
standards in humans.  It states, no big news, that no chemical has been
found to cause thyroid carcinoma in humans. 

It is clear that certain ionizing radiations cause thyroid cancer, and
external x-ray beams are well known for this.  I don't know why, rad for
rad, I-131 is less carcinogenic to the thyroid than x-rays.  Perhaps because
of the beta, I-131 kills cells that concentrate it, and dead cells don't
become cancer cells.   One may have to substantially deplete the population
of thyroid cells before cancer is evident.  There is some question of
whether Graves' disease does or does not predispose to thyroid cancer.  The
difference in study results may be due to how the Graves' disease was
treated.  Graves' glands quickly destroyed with I-131 cannot give rise to
thyroid cancer because no thyroid tissue remains.  Partial treatment with
I-131, or non-radioactive drug treatment, both of which leave living thyroid
cells, may predispose the patient to cancer.  However, this is only
conjecture on my part.

Ciao, Carol

Carol S. Marcus, Ph.D., M.D.
<csmarcus@ucla.edu>

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