Thyroid Research Thyroid Research Archive Thyroid Cancer

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.