Thyroid radioiodine scanning has little
value in patients with thyroid carcinoma before first radioiodine
therapy
(March 2005)
The background of the study. Many patients with
thyroid carcinoma are treated with iodine-131 (I-131) after surgery
to destroy any remaining normal thyroid tissue and carcinoma. Thyroid
scans are often done before I-131 is given, but their value is debated.
In this study, I-131 uptake in the neck and serum thyroglobulin
were measured before I-131 therapy, and the results were compared
with the results of post-therapy scans.
How the study was done. The study subjects were
875 patients with papillary or follicular thyroid carcinoma who
were treated with I-131. After total thyroidectomy and cessation
of thyroid hormone therapy, serum thyroglobulin and neck uptake
of a low dose of I-131 were measured. The patients were then treated
with I-131, and a whole-body scan was done two to five days later.
The results of the study. The whole-body scans
performed after therapy with I-131 revealed only thyroid remnants
in 708 patients (81 percent), tumor in lymph nodes in 70 patients
(8 percent), distant tumor in 38 patients (4 percent), and both
lymph-node and distant tumor in 6 patients (1 percent). Ninety-one
percent of these 822 patients had detectable thyroid uptake of I-131
and serum thyroglobulin values ≥1 ng/ml before I-131 therapy.
The post-therapy scans were negative in 53 patients (6 percent),
all of whom had serum thyroglobulin values <1 ng/ml and no detectable
thyroid uptake of I-131 before I-131 therapy.
The conclusions of the study. Most patients with
thyroid carcinoma treated by total thyroidectomy have some remaining
thyroid tissue, and therefore I-131 scanning before I-131 therapy
is not necessary.
The original article. Salvatori M, Perotti G,
Rufini V, Maussier ML, Dottorini M. Are there disadvantages in administering
131I ablation therapy in patients with differentiated
thyroid carcinoma without a preablative diagnostic 131I
whole-body scan? Clin Endocrinol (Oxf) 2004;61:704-10.
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