RE: Well logging/Tracer Operations

[mozley@darius.pet.upenn.edu (P. David Mozley)]

>. . . it is normal practice to call for a chromosome abberation test, which
>should be able to determine even quite 'old' excessive exposures . . .
>      If the dose was sufficient to cause tumour, the effects might still be
>detectable, some years later.
>             Roger Gelder

There may be a fundamental problem with the question in this case that
could limit the usefulness of chromosomal abberation data.

Mediasteinal tissues like the thymus may not be the target organs for any
of the radionuclides that were listed as potential hazzards for loggers,
with the possible exception of I-131. But, if there were a significant
lifetime history of exposure to I-131, then simple thyroid function tests
should be the most reliable indicators of their magnitude.  Even if thyroid
disease could be documented, postulating a relationship would be
indefensible because carcinoid of the thymus is not associated with
iatrogenic exposure to therapuetic doses of I-131.

The alimentary tract and the renal system are usually exposed to the
highest levels of radiation from ingested radionuclides.  Carcinoids are
rare, but their most common origin is in the alimentary tract, where they
make up less than 2% of all GI tumors.  This patient did not develope
carcinoid near the site of highest dosimetry. If the patient did not
develope the disease in the most suseptible organ to developing the disease
even though that organ was likely to have been exposed to the most ionizing
radiation, it follows then that the developement of the disease in a less
suseptible, less exposed tissue was not induced by internal radiation.

Carcinoids of the thymus are very rare.  Of the 20 to 30 cases that have
been reported in Med-Line referenced journals since the 1960's, none I am
aware of were explicitly documented as having been exposed to excess
ionizing radiation.
A more promising venue of clincial investigation in this case might be to
dig for a family history of endocrine neoplasia.  Exploration of the most
common cause of a very rare disorder seems required before testing
hypotheses about novel external triggers like low level radiation exposure.

It is quite appropriate for patients and their physicians to search for
environmental factors which may have contributed to the development of
their diseases, particularly when, as in this case, the disease is very
rare.  In this case, it seems that a hypothesis about exposure to ionizing
radiation is in the process of being explored, but it is unlikely that
supportive evidence will be found.  I hope this conclusion will help the
patient to feel better.  It will be sad for him to go on thinking that his
work habits were to blame for his most unfortunate health problems.  I
would not promote the idea that prevention of the disease was under his
control by recommending a bunch of tests that may or may not be indirectly
related to radiation exposure anyway.

Think about it.

mozley@darius.pet.upenn.edu