Recombinant Human Thyrotropin-Stimulated Serum Thyroglobulin Combined with Neck Ultrasonography Has the Highest Sensitivity in Monitoring Differentiated Thyroid Carcinoma

Abstract

Recombinant human TSH (rhTSH)-stimulated thyroglobulin (Tg) measurement and (131)I whole body scan (WBS) have been validated as informative tests in the postsurgical follow-up of differentiated thyroid carcinoma. We report the diagnostic accuracy of Tg measurement and diagnostic WBS, alone or in combination, after rhTSH stimulation in a retrospective, consecutive series of patients undergoing follow-up for differentiated thyroid cancer. Routine procedures also include neck ultrasound in every patient and post-therapy WBS when indicated. We studied 340 consecutive patients with differentiated thyroid carcinoma, previously treated with near-total thyroidectomy and (131)I thyroid ablation, scheduled for routine diagnostic tests. At baseline on L-T(4)-suppressive therapy, 294 patients had undetectable (<1 ng/ml) serum Tg and negative anti-Tg autoantibodies (TgAb), 25 patients had undetectable serum Tg and positive TgAb, and 21 patients had detectable serum Tg and negative TgAb. These patients were tested for the presence of active disease by rhTSH stimulation. The results of our study showed that rhTSH-stimulated Tg alone had a diagnostic sensitivity of 85% for detecting active disease and a negative predictive value (NPV) of 98.2%. After adding the results of neck ultrasound, sensitivity increased to 96.3%, and the NPV to 99.5%. rhTSH-stimulated WBS had a sensitivity of only 21% and a NPV of 89%. The combination of rhTSH-stimulated Tg and WBS had a sensitivity of 92.7% and a NPV of 99%. We conclude that the rhTSH-stimulated Tg test combined with neck ultrasonography has the highest diagnostic accuracy in detecting persistent disease in the follow-up of differentiated thyroid carcinoma. A detectable level of serum Tg on L-T(4), its conversion from undetectable to detectable after rhTSH, and/or a suspicious finding at ultrasound will allow the identification of patients requiring therapeutic procedures without the need for diagnostic WBS.

Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Taskforce

“…h RxWBS is posttreatment whole-body scan done 5 to 8 days after therapeutic 131 Cervical ultrasonography. Cervical ultrasonography is highly sensitive in the detection of cervical metastases in patients with differentiated thyroid cancer (208). Cervical metastases occasionally may be detected by neck ultrasonography even when TSH-stimulated serum thyroglobulin levels remain undetectable (200).…”

Management of low-risk patients with thyroid carcinoma and detectable thyroglobulin on T4 after thyroidectomy and ablation with iodine-131

“…No DxWBS was performed in the present series and we directly administered a therapeutic dose of 131 I (followed by RxWBS) to patients with negative US and CT. DxWBS showed ectopic uptake in only 5 to 33% of patients with detectable Tg on T4 in other series (13)(14)(15)(16). We therefore considered DxWBS to be of little value in this situation.…”

Thyroglobulin levels before radioactive iodine therapy and dynamic risk stratification after 1 year in patients with differentiated thyroid cancer

“…sTg (in the presence of TSH > 30 mUI/l) is the best means of detecting remnant thyroid tissue after initial treatment in patients with DTC. Elevated TSH, whether endogenous or recombinant, stimulates the uptake of iodine and promotes release of more Tg from thyroid remnants and metastatic lesions (23), thereby improving the accuracy of the scan. However, despite its importance as a biochemical marker for monitoring DTC, serum Tg is not classically used as an initial prognostic value.…”