PET/CT before Radioactive iodine ablation ? bad idea ?



A

anita1766

Guest
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
 
[email protected] wrote:

>
> 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

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
 
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
 
[email protected] wrote:

> <snipped>
>
> 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.

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.
 
J <[email protected]> wrote:

> [email protected] wrote:
>
> > <snipped>
> >
> > 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.
>
> 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.

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.

--
madiba
 
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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