Usefulness of repeated recombinant human thyrotropin-stimulated thyroglobulin test in the post-surgical follow-up of very low-risk patients with differentiated thyroid carcinoma.

Abstract

The European Thyroid Association (ETA) and the American Thyroid Association (ATA) guidelines identify subgroups of patients affected by thyroid carcinoma in whom, due to a low risk of recurrence, radioiodine ablation is not indicated. These patients are referred to as "very low-risk" according to the ETA consensus and "low-risk" patients according to the ATA guidelines. The recommended post-surgical follow-up of these patients is based upon periodical measurements of serum thyroglobulin (Tg) on levothyroxine therapy and neck ultrasound (US). To evaluate the usefulness of recombinant human (rh)-TSH Tg test and its repetition 2-3 yr afterwards in very low-risk patients. We consecutively enrolled 32 patients with undetectable anti-Tg antibodies. Basal serum Tg levels was undetectable in all patients. Following rhTSH serum Tg remained undetectable in 23 (71.9%) patients (UP) and was >1.0 ng/ml in 9 (DP). US and whole body scan, revealed lymph node metastasis in 4/9 DP patients. A second rhTSH stimulation test (36.9±3.5 months later) was performed in all UP and in 5 DP patients without proven recurrences. All the UP and 4/5 formerly DP patients showed undetectable Tg stimulation. Our results suggest that rhTSH Tg test may be helpful in very low-risk patients, given its ability to differentiate those who may be considered "free of disease" from those who require further investigation and treatment. Repeated rhTSH Tg tests may be indicated only in patients with detectable serum Tg at prior stimulation testing.