Importance of measurement of thyroglobulin and anti-thyroglobulin antibodies in differentiated thyroid cancer.

Differentiated thyroid cancers include papillary and follicular carcinomas, both originating from follicular epithelium. Treatment of choice is usually total or near total thyroidectomy, followed by ablative radioiodine I-131 treatment, and by the long term administration of thyroid hormone. Despite its excellent prognosis, recurrent disease does occur in approximately 20-40% of patients. Guidelines for the follow-up management of differentiated thyroid cancer are commonly based on circulating thyrogobulin measurement in the complete absence of eutopic thyroid tissue. A retrospective review was conducted on 116 patients (66 papillary and 50 follicular carcinoma, mean age 51.2 years) who had undergone total or near total thyroidectomy and radioactive iodine remnant ablation. Serum thyroglobulin (Tg) and anti-thyroglobulin antibodies (TgAb) levels were measured preoperatively, 1 month after thyroidectomy (before I-131 treatment) and 6 and 12 months after ablation therapy (Tg 1, TgAb1 and Tg2, TgAb2, respectively). During one year of follow-up, in a total of 24 patients (21%) recurrent disease were confirmed by ultrasonography and whole-body-scanning, mostly. It was found significant correlation between serum Tg levels (measured preoperatively and postoperatively) and recurrent diseases (p<0.05), while serum TgAb levels did not have any statistical significance. However, in multivariate regression analysis only Tg levels measured 12 months after the therapy (Tg2) remained a significant predictor of recurrent disease (p=0.008). Although a high Tg level before surgery does not indicate that tumor is present, in the postoperative period and after ablative therapy Tg has proven predictive value because stimulated Tg levels above 10ng/ml confirmed that indicate residual or recurrent cancer, and its periodically measurements is recommended.