Effect of Postoperative¹³¹I Treatment on Thyroglobulin Measurements in the Follow-up of Patients with Thyroid Cancer

Abstract

Correlation of serum thyroglobulin (Tg) levels with recurrent cancer was performed in 200 patients who had undergone a subtotal thyroidectomy for well-differentiated thyroid carcinoma. Patients were divided into three groups: (1) those not treated postoperatively with radioactive iodine, (2) those treated with low dose (30 mCi) radioactive iodine, and (3) those treated with high dose (50-250 mCi) radioactive iodine. Tg levels proved to be reliable in detecting recurrent thyroid cancer regardless of the dose of radioactive iodine given postoperatively. These results reinforce the recommendation of using the Tg assay as the primary method of following these patients postoperatively, even when there was less than a total thyroidectomy and ablation with radioactive iodine.

131I Treatment of 131I Negative Whole Body Scan, and Positive Thyroglobulin in Differentiated Thyroid Carcinoma: What Is Being Treated?

“…The value also depends on the method of assay and the presence of antithyroglobulin antibodies. Tg levels also depend on thyrotropin (TSH) values (22)(23)(24).…”

Is Serum Thyroglobulin a Useful Marker for Thyroid Cancer in Patients Who Have Not Had Ablation of Residual Thyroid Tissue?

“…We have previ¬ ously reported on its use and shown differences depending on whether measurements are made while the patient is taking thyroxine, or not (17). Several investigators have criticized the use of Tg measurement in patients with resid¬ ual thyroid, since all thyroid is potentially capable of mak¬ ing and secreting Tg (18)(19)(20)(21). In this investigation, we be¬ lieve that Tg provides information that complements the clinical examination.…”

“…It would be reassuring to have some method of following these patients in addition to clinical examination. Since Van Herle and colleagues confirmed that Tg could be measured by radioimmunoas¬ say (30), serum Tg measurement has proven to be a very useful test in patients who are athyreotic, it has both high sensitivity and specificity (16,17,18,31). We have previ¬ ously reported on its use and shown differences depending on whether measurements are made while the patient is taking thyroxine, or not (17).…”

“…FT4 was measured by a two-step immunoradiometric as¬ say, whose characteristics have been reported previously (22). The normal range was 0.8-2.0 ng/dL (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) pmol/L), quantitatively in the presence of anti-Tg (25). Originally the antibodies were measured by a method developed at Stanford (26), subsequently by the Kronus assay.…”

“…In patients who have had thyroid ablation, serum thyroglobulin (Tg), measured while the patient is taking L thyroxine, is a useful "cancer" marker with high sensitivity and specificity (16,17). Because Tg is produced by all thyroid tissue, normal and abnormal, it is stated that it has less value in follow-up of those with residual thy¬ roid (18)(19)(20)(21). We have evaluated serum Tg measurements in 47 patients with thyroid cancer who have not had ab¬ lation of residual thyroid tissue.…”