Thyroid Research Thyroid Research Archive Thyroid Cancer

Patients with thyroid cancer who have low serum thyroglobulin concentrations after surgery have a low risk of tumor recurrence

(July 2005)

The background of the study. High serum thyroglobulin concentrations indicate the presence of persistent or recurrent tumor in patients with papillary or follicular carcinoma of the thyroid. This study was done to determine whether measurements of serum thyroglobulin at the time of initial radioactive iodine (I-131) therapy predict recurrence in patients with these tumors.

How the study was done. The study subjects were 268 patients with thyroid carcinoma localized to the neck at the time of initial surgery and I-131 therapy. Serum thyroglobulin was measured five to six weeks after surgery, during which time no thyroid hormone had been given and hypothyroidism developed. The patients were given I-131 to destroy any remaining thyroid tissue and then given thyroid hormone. Subsequently, the patients were evaluated for tumor recurrence at 6- to 12-month intervals.

The results of the study. At the time of I-131 therapy, 64 of the 268 patients (24 percent) had a serum thyroglobulin value >10 ng/ml, of whom 27 (42 percent) had a recurrence during follow-up. The serum thyroglobulin value was >2 to 10 ng/ml in 79 patients, of whom 6 (8 percent) had a recurrence, and the value was ≤2 ng/ml in 125 patients, of whom 2 (2 percent) had a recurrence.

The conclusions of the study. Patients with thyroid carcinoma who have a low serum thyroglobulin concentration when hypothyroidism is present at the time of I-131 therapy after surgery are unlikely to have a recurrence of their tumor.

The original article. Kim TY, Kim WB, Kim ES, Ryu JS, Yeo JS, Kim SC, Hong SJ, Shong YK. Serum thyroglobulin levels at the time of 131I remnant ablation just after thyroidectomy are useful for early prediction of clinical recurrence in low-risk patients with differentiated thyroid carcinoma. J Clin Endocrinol Metab 2005;90:1440-5.