Although the treatments for most forms of thyroid cancer
-- surgery, radioiodine, and thyroixine therapy -- are very
effective, almost one-third of patients have a recurrence of
their disease later in life. So it is important for thyroid
cancer patients to be followed by their doctor for the rest
of their lives, typically every 6 to 12 months. The earlier
recurrent cancer is detected, the easier it is to treat.
The tools to detect recurrent thyroid cancer are a doctor's
examination; the thyroglobulin blood test; and for some patients,
the radioactive iodine scan, neck sonogram, and other imaging
studies.
The doctor typically asks about symptoms (such as difficulty
swallowing, persistent hoarseness, or pain in the front of the
neck) and feels the neck carefully to detect any lumps
that might indicate reappearance of disease.
The thyroblobulin (Tg) blood test detects this protien,
which is only made by thyroid cells -- either from thyroid
cancer or remaining normal thyroid tissue. Tg testing is more
sensitive when there is thyroid stimulating hormone (TSH) around
to promote thyroid tissue to make more Tg. In most patients,
this testing is very helpful, but one in five thyroid cancer
patients have antibodies in their blood that make it impossible
to detect Tg accurately with current testing techniques.
Because thyroid cells take up iodine, radioactive iodine
can reveal the presence of some recurrent thyroid cancers.
Radioiodine scans are only accurate when there is thyroid stimulating
hormone (TSH) around to promote iodione uptake by thyroid tissue.
Until recently, the only way to provide the TSH stimulation
needed for testing was to temporarily stop a patient's thyroxine
treatment so their own pituitary would make more TSH. Of
course, this causes all of the symptoms of thyroid hormone deficiency
(hypothyroidism).
