RE: 131-I and pregnancy

[Karin Gordon <KGordon@exchange.hsc.mb.ca>]

I fully agree with Dr. Gibbs.  

For thyroid cancer patients, another good reason for delaying the
initiation of a pregnancy for six months or a year (preferable, in my
opinion) post thyroid remnant ablation radionuclide therapy is the fact
that the patient may already have or may develop metastatic disease.  If
metastases  occur, the patient will require at least one re-treatment
with 100+ millicuries of I-131, often within the first year or two after
the initial therapy.  While thyroid cancer has a very high cure rate,
people do die from it (we lost a patient just a few weeks ago).  You do
not want to compromise your treatment options, or have a pregnant
patient requiring treatment for metastatic disease go through the
heartbreak of having to choose  between her life and the life of the
baby she is carrying.

For hyperthyroid patients undergoing radionuclide therapy, their thyroid
hormone status changes significantly post therapy, and many of these
patients eventually become hypothyroid and require daily exogenous
thyroid hormone replacement.  It seems to me that the patient should be
counselled to work closely with her endocrinologist if she is
considering pregnancy, as her thyroid hormone levels will have to be
closely monitored during the pregnancy, with very carefully adjusted
thyroid hormone replacement initiated if necessary.



>.edu]
>Sent: 	September 23, 1998 2:31 PM
>To: 	Multiple recipients of list
>Subject: 	Re: 131-I and pregnancy
>
>As a medical radiobiologist I must take issue with the 
>previously posted response to the question: How long should 
>a patient wait to become pregnant after 131-I therapy for 
>thyroid cancer or hyperthyroidism?
>The issue is NOT radiation dose to the fetus.  It is dose 
>to the maturing follicle in the ovary.  This dose at the 
>time of administration and shortly thereafter is 
>substantially greater than the dose later to the embryo 
>from radioisotope accumulated in the mother's body. Current 
>data suggest that the maturing follicle is almost as 
>sensitive as the early embryo.  Therefore, one should wait 
>for all maturing follicles at the time of irradiation to 
>ovulate.  This interval is open to some question.  One can 
>find support for waiting from 1 to 12 months, as has been 
>recommended to the questioner.  In any event, the wait 
>should be "several menstrual cycles."
>Hope this helps.
>***********************************************************
>S. Julian Gibbs, DDS, PhD               Voice: 615-322-3190
>Professor of Radiology                    FAX: 615-322-3764 
>Dept. of Radiology & Radiological Sciences
>Vanderbilt University Medical Center
>Nashville TN 37232-2670 Email:s.julian.gibbs@Vanderbilt.Edu
>
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