Serum Thyroglobulin Levels after Thyroxine Withdrawal in Patients with Low Risk Papillary Thyroid Carcinoma

We hypothesized that elevated levels of serum thyroglobulin (Tg) are frequently found as the only index of residual neoplasm in patients with low-risk papillary thyroid carcinoma. The records of patients operated on for papillary thyroid carcinoma over a 2-year period were reviewed, and the patients were allocated to risk groups by a validated staging method that does not include Tg levels. Of the 35 patients who manifested a low-risk carcinoma, 9 (26%) exhibited elevated Tg concentrations (11-53 ng/mL) during thyroxine withdrawal after therapies, while clinical, scintigraphic, and radiographie studies at least 1 year later showed no evidence of tumor. Prior scintigraphic imaging of therapeutic doses of ¹³¹I in 8 of 9 patients demonstrated no distant metastases, further confirming the low-risk status of this group. The staging method predicts that only 0.9% of patients with low-risk papillary carcinoma will have a cause specific death in 20 years. Elevated Tg concentrations have not been shown to forecast independently the survival of patients with low-risk papillary carcinoma. Thus, although frequently encountered, elevated Tg concentrations are unlikely to predict shortened survival in patients with papillary carcinoma for whom low risk has been determined from other data.