New imaging technique for rare thyroid cancer
6 Octpber 2008
A new imaging approach for identifying a rare form of thyroid cancer
that is typically hard to diagnose has been developed by researchers at
the University of Iowa.
Accurate diagnosis of the cancer, known as poorly differentiated
thyroid cancer (PDTC), can help physicians choose the best treatment for
the patient. The study results, which appear in the Sept 18 issue of
The New England Journal of Medicine, also raise the possibility of
extending the use of radioiodine therapy to thyroid cancers where the
thyroid gland cannot be surgically removed.
Radioiodine therapy takes advantage of the fact that thyroid cells
are the only tissue that takes up iodine and thus delivers radioactive
iodine to cancerous thyroid tissue. This targeted radiation therapy
often is used to destroy any cancerous thyroid cells that remain after
removal of the thyroid gland — an approach often used to treat thyroid
Malik Juweid, MD, University of Iowa professor of radiology in the
Roy J and Lucille A Carver College of Medicine, and colleagues used a
compound called thyrotropin to stimulate radioactive iodine uptake by
tumour cells in a patient who had cancer of unknown origin.
Concentration of radioiodine by the patient's tumour cells indicated
that the thyroid was the primary site of patient's cancer and confirmed
the diagnosis of PDTC. The stimulated radioiodine scan also showed that
this patient's cancer cells did not take up enough radioactive iodine
for this to be a good way to treat the tumour and thus a different
treatment option, external beam radiation, was chosen.
"Typically radioiodine is used in two ways — as a scanning tool to
visualise where thyroid tumour cells are in the patient and as a way to
deliver radiation therapy to kill residual cancer cell after removal of
the thyroid gland" Juweid explained.
Although in this case the PDTC cells did not take up enough
radioiodine to allow delivery of therapeutic doses of radiation, many
PDTCs do take up large amounts of iodine. The study suggests that
boosting uptake of radioiodine with thyrotropin might be a way to extend
the use of radioiodine therapy to treat thyroid cancer even in cases
where the thyroid gland cannot be surgically removed.