Fwd: I-131 Dosimetry

[Ccja@aol.com]

Jocelyn

Thanks for your (now standard) great response. I might only add that it would
be more useful, if you were to include the addresses (email, and other) of
your sources, or at least a more specific ID. E.g., Mike Stabin is in the
Radiation Internal Dose Information Center, at the Oak Ridge Institute for
Science and Education. That Center is funded by the USFDA and the USDOE, to
provide answers to these sorts of questions, free of charge, to anyone.
chris alston
ccja@aol.com

---------------------
Forwarded message:
From:	jtowson@NUCMED.RPA.CS.NSW.GOV.AU (Jocelyn Towson)
Sender:	medphys@LISTS.WAYNE.EDU (Medical Physics Listserver)
Reply-to:	MEDPHYS@LISTS.WAYNE.EDU (Medical Physics Mailing List)
To:	MEDPHYS@LISTS.WAYNE.EDU (Multiple recipients of list MEDPHYS)
Date: 97-08-31 20:14:46 EDT

>>From: SCOTT DUBE <SDUBE@QUEENS.ORG>
>>Subject:      I-131 Dosimetry
>>To: Multiple recipients of list MEDPHYS <MEDPHYS@cwis-20.wayne.edu>
>>
>>Here's an interesting case of an unfortunate patient.  This 60 year old
>>male has been treated for post-thyroidectomy for follicular
>>adenocarcinoma with metastasis to this T-11 vertebral body.  His
>>treatment history includes four separate oral doses of iodine-131:
>>
>>Jan 1996 - 150 mCi
>>Jun 1996 - 150 mCi
>>Dec 1996 - 150 mCi
>>Jul 1997 - 150 mCi
>>
>>There is still uptake in the T-11 vertebral body.  The nuclear medicine
>>physician hs two question:
>>
>>1.  Spinal Cord Dose - How can I estimate the dose to the spinal cord?  Is
>>it cumulative?
>>
>>2.  Bone Marrow Dose - I can estimate the bone marrow dose for each
>>treatment using published formalism, but again, I don't know if the dose is
>>cumulative.  Doesn't the bone marrow regenerate every few months?
>>
>>Any information or leads would be appreciated.  Thanks.

We have a similar patient who presented in 1995 with paraplegia from spinal
cord compression at T8.  He recovered movement of his limbs after surgery,
and has since had seven I-131 therapies,average 200 mCi each, for
metastatic follicular thyroid cancer (plus one external beam treatment of
30 Gy after the first I-131 treatment). Early in the piece we asked Mike
Stabin from RIDIC for help in estimating the dose to the spinal cord: the
result was an average cord dose of about 1.7 Gy/6.5 GBq administered,
adjacent to T8 (ref J Nuc Med 37(5): May 1996 Suppl,90P).  An MRI showed
1-2mm of CSF between the vertebral body and the cord which seems to provide
enough protection because of the short range of the I-131 betas.  (Unlike
Sr-89).
We treated this patient again last week; he has steroid cover prescribed
each time.  He looks pretty good but still has uptake in T8 and now a few
other sites.  We have a number of patients who have had multiple treatments
4-5 months apart, some to over 3 Ci total.
Transient bone marrow suppression after I-131 therapy for thyroid cancer is
mentioned in many papers including those of Clarke (Eur J Nucl Med
18:984-991,1991) and van Nostrand et al (J Nucl Med 27:1519-1527), 1986.  A
case of significant bone marrow suppression after 250mCi was reported by
Bushnell et al (J Nuc Med 33:2214-2221, 1992), but the patient had low
fluid intake and poor renal output.
Hope this helps.
Regards,

Jocelyn Towson, RSO
Dept of PET & Nuclear Medicine
Royal Prince Alfred Hospital
Camperdown, NSW 2050
Australia

tel [national]  02 9515 8011    [international] 61 2 9515 8011
fax [national]  02 9515 6381    [international] 61 2 9515 6381
email   jtowson@nucmed.rpa.cs.nsw.gov.au