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 (DTC0 has been based upon serum thyroglobulin (Tg) measurement and I-131 whole body scan (I-131-WBS) after thyroid hormone (T-4) treatment withdrawal. However, I-131-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 I-131-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 I-131 ablation, with no uptake outside the thyroid bed on the post-ablative I-131-WBS (low-risk patients) were enrolled. Methods: Measurement of serum Tg and I-131-WBS after rhTSH stimulation, and ultrasound examination (US) of the neck. Results: rhTSH-stimulated Tg was less than or equal to 1 ng/ml in 78 patients (Tg-) and > 1 ng/ml (Tg+) in 21 patients, including 6 patients with Tg levels > 5 ng/Ml. I-131-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 I-131-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.