PET/CT before Radioactive iodine ablation ? bad idea ?

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anita1766@yahoo.com - 26 Jan 2004 19:42 GMT

Hello all,

I have been feeling so absolutely terrible, pain i the neck is constant and
left sided headaches and then there is the loss of appetite, breathing
problems and just plain FATIGUE. I did not know I could feel SO tired.
And yet by all accounts I am doing alright. My Tg is at 3 post thyroidectomy
and neck dissection, compared to 78 prior. My TSH is close to 1 and T3 and
T4 are normal, but I feel like death armed over. Not depressed-oh no, just
plain TIREd and in pain.

I asked my doctor for a PET/CT and my onco is currently scheduling it. I
have a horrible feeling that a LOT of areas are going to light up - possibly
in my lungs and head. My intuitions have been pretty much on target all this
while...I just hope I am really really wrong this time.

So here is my question: Will getting a PET/CT (just FDG - no iodine
contrast) affect uptake of radioactive iodine in anyway ? I am going to
start my Low iodine diet (for my radioactive ablation ) next week.

Thanks for listening.
Anita

Papillary Carcinoma -diagnosed Jun 03
TT and MRND surgery- Nov 2003
Dermatofibrosarcoma Protuberans of the neck -diagnosed and excised Nov 2003
Family history of anaplastic thyroid carcinoma- maternal grandmother

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J - 28 Jan 2004 02:36 GMT

> I have been feeling so absolutely terrible, pain i the neck is constant and
> left sided headaches and then there is the loss of appetite, breathing
[quoted text clipped - 20 lines]
> Dermatofibrosarcoma Protuberans of the neck -diagnosed and excised Nov 2003
> Family history of anaplastic thyroid carcinoma- maternal grandmother

I'm sorry you are having a rough time, Anita.
Are you worried you might have anaplastic thyroid cancer?
No one's answered your question.
Either they missed your post or it's too complicated.
Can you contact the endocrinologist and ask your question about contrast and
iodine?

I'm wondering if the neck surgeries could maybe have caused apnea?
(that could account for fatigue). You would need an overnight sleep study to
find out for sure.

Keep in touch, luv.

Hugs
J

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anita1766@yahoo.com - 28 Jan 2004 18:34 GMT

Hello J,
I know, maybe people are getting tired of hearing me complain. But I was
hoping someone with medical training lurking on these boards might respond.
My endo says he does not know and is right now concerned only with
Radioactive iodine ablation. The sleep -onset breathing issues have been
troubling me since about April much before even my Hashimotos diagnosis, let
alone thyroid cancer. First they said its anxiety, then they said its the
thyoxine and then they said its the cancer.
I know I dont have anaplastic thyroid cancer, but I think I have a strong
tendency to developing it. From what I understand papillary and anaplastic
are the 2 ends of the same spectrum. The same genes that are mutated in
papillary seem to be implicated in anaplastic. And I have read that about
30% of papillary eventually turns to dedifferentiated thyca. I have pubmed
links for these studies, do u want me to pos them ? I am definitely
concerned that this sleep disordered breathing (not apnea really) is a
manifestation of mets somewhere in my lungs or my medulla (I have a pretty
big lump at my skull base left side).

I did get an overnight sleep study done and I hope my neurologist can get
to the bottom of it. The results are not back yet. She seemed to find the
case interesting...
I am tired of feeling like this. I really hope it would end soon.
hugs to you too
Anita

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J - 28 Jan 2004 19:06 GMT

> <snipped>
>
[quoted text clipped - 6 lines]
> contrast) affect uptake of radioactive iodine in anyway ? I am going to
> start my Low iodine diet (for my radioactive ablation ) next week.

Call the Nuclear Medicine Unit of the lab/department/hospital of where the
radioactive ablation is going to be done.
I don't know if they will first have to know which you are having PET or CT and
when.

J.

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madiba - 28 Jan 2004 23:48 GMT

> > <snipped>
> >
[quoted text clipped - 10 lines]
> radioactive ablation is going to be done. I don't know if they will first
> have to know which you are having PET or CT and when.

PET's FDG has nothing to do with iodine, its a sugar. Its for non-iodine
sensitive thyroid tumors, so a spread of the papill. tumor will not be
documented.
The OP wrote that iodine (contrast) would not be given in the CT..
If there is still so much uncertainty then do it after the radioactive
iodine treatment.

Signature

madiba

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anita1766@yahoo.com - 29 Jan 2004 22:38 GMT

Yeah, I called the endo who is going to be overseeing my ablation and he has
not returned my call. It been more than a week.
Anyway, I know PET is done with FDG - (2-deoxy-2-[18F]fluoro-D-glucose), for
non-thyroid tumors. But it also picks up de-differentiated thyroid cancer
cells (ie., cells which are in the process or have already lost their
function -so do not take up iodine very well. These cells DO tend to take up
glucose for their rapid growing- anaplastic are those kind of thyroid
cells).
Besides I also have a second cancer, on the neck- which may or may not be in
a bad state- I do remember that this cyst like thing grew rather rapidly in
the last 6-8 months and during surgery they found it was something called
DFSP.
So I was looking to the PET/CT (its a combination of PET AND a CT,
non-contrast in my case) to see if I have any cells that are growing rapidly
and go from there.

I just wanted to make sure that the
a)exposure to radioactivity in the FDG does not make the cells resistant to
the radiation that is going to be used for ablation
b)the flourine in the FDG does not affect iodine uptake
I guess I will have to keep looking for research...

Here is a link to use of PET for thyroid
cancer...http://www.health-imaging.com/03b_whatisfdg.html

Thanks all
Anita

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