Utility of Stimulated Thyroglobulin in Reclassifying Low Risk Thyroid Cancer Patients’ Following Thyroidectomy and Radioactive Iodine Ablation: A 7-Year Prospective Trial

Abstract

ContextFollowing total thyroidectomy and radioactive iodine (RAI) ablation, serum thyroglobulin levels should be undetectable to assure that patients are excellent responders and at very low risk of recurrence.ObjectiveTo assess the utility of stimulated (sTg) and non-stimulated (nsTg) thyroglobulin levels in prediction of patients outcomes with differentiated thyroid cancer (DTC) following total thyroidectomy and RAI ablation.MethodA prospective observational study conducted at a University Hospital in Saudi Arabia. Patients diagnosed with differentiated thyroid cancer and were post total thyroidectomy and RAI ablation. Thyroglobulin levels (nsTg and sTg) were estimated 3–6 months post-RAI. Patients with nsTg <2 ng/ml were stratified based on their levels and were followed-up for 5 years and clinical responses were measured.ResultsOf 196 patients, nsTg levels were <0.1 ng/ml in 122 (62%) patients and 0.1–2.0 ng/ml in 74 (38%). Of 122 patients with nsTg <0.1 ng/ml, 120 (98%) had sTg levels <1 ng/ml, with no structural or functional disease. sTg levels >1 occurred in 26 (35%) of patients with nsTg 0.1–2.0 ng/ml, 11 (15%) had structural incomplete response. None of the patients with sTg levels <1 ng/ml developed structural or functional disease over the follow-up period.ConclusionSuppressed thyroglobulin (nsTg < 0.1 ng/ml) indicates a very low risk of recurrence that does not require stimulation. Stimulated thyroglobulin is beneficial with nsTg 0.1–2 ng/ml for re-classifying patients and estimating their risk for incomplete responses over a 7 years follow-up period.

Clinical and Laboratory Aspects of Thyroglobulin and Thyroglobulin Antibody in Differentiated Thyroid Carcinoma

“…22 An observational study in Saudi Arabia reported that 98.0% of DTC patients with a serum Tg concentration below 0.1 ng/ml estimated at 3-6 months post-total thyroidectomy and RAI had no structural or functional disease, which indicates a very low risk of cancer recurrence. 23 This finding was supported by another study that found a significant structural recurrence rate, which was high (30.0%) among DTC patients with a stimulated post-operative thyroglobulin level of more than 2 ng/ml. 24 On the other hand, a retrospective study in 570 DTC patients demonstrated that a low or undetectable postoperative Tg level did not rule out metastases in early stage malignancy; 90.2% of metastatic patients had serum Tg levels below the detection limit.…”