Serum thyroglobulin and 131I whole body scan after recombinant human TSH stimulation in the follow-up of low-risk patients with differentiated thyroid cancer

Objective: The 'standard' postoperative follow-up of patients with differentiated thyroid cancer (DTC) has been based upon serum thyroglobulin (Tg) measurement and ¹³¹I whole body scan (¹³¹I-WBS) after thyroid hormone (T₄) treatment withdrawal. However, ¹³¹I-WBS sensitivity has been reported to be low. Thyroid hormone withdrawal, often associated with hypothyroidism-related side effects, may now be replaced by recombinant human thyroid stimulating hormone (rhTSH). The aim of our study was to evaluate the diagnostic accuracy of ¹³¹I-WBS and serum Tg measurement obtained after rhTSH stimulation and of neck ultrasonography in the first follow-up of DTC patients. Design: Ninety-nine consecutive patients previously treated with total thyroidectomy and ¹³¹I ablation, with no uptake outside the thyroid bed on the post-ablative ¹³¹I-WBS (low-risk patients) were enrolled. Methods: Measurement of serum Tg and ¹³¹I-WBS after rhTSH stimulation, and ultrasound examination (US) of the neck. Results: rhTSH-stimulated Tg was ≤ 1 ng/ml in 78 patients (Tg-) and > 1 ng/ml (Tg+) in 21 patients, including 6 patients with Tg levels > 5 ng/ml. ¹³¹I-WBS was negative for persistent or recurrent disease in all patients (i.e. sensitivity = 0%). US identified lymph-node metastases (confirmed at surgery) in 4/6 (67%) patients with stimulated Tg levels > 5 ng/ml, in 2/15 (13%) with Tg > 1 <5 ng/ml, and in 2/78 (3%) who were Tg-negative. Conclusions: (i) diagnostic ¹³¹I-WBS performed after rhTSH stimulation is useless in the first follow-up of DTC patients; (ii) US may identify lymph node metastases even in patients with low or undetectable serum Tg levels.