Published data on recombinant human thyrotropin- (rhTSH-) stimulated iodine-123 (123I) diagnostic whole-body scintigraphy (DxWBS) in differentiated thyroid cancer (DTC) surveillance after initial treatment are limited. We sought to evaluate this modality's diagnostic value in this setting.
We retrospectively compared rhTSH-stimulated 123I DxWBS results with DTC status concurrently determined by stimulated serum thyroglobulin (Tg) measurement, neck ultrasonography, and other imaging studies. Disease was considered present based on stimulated Tg level ≥1 μg/L without interfering Tg autoantibodies with or without positive imaging or biopsy-proven DTC. We also compared scan positivity and disease detection rates of rhTSH-stimulated DxWBS scans obtained with 123I with those acquired with iodine-131 (131I) during the same period. The sample comprised 105 consecutive totally thyroidectomized patients undergoing rhTSH-aided DxWBS with I-123 (n = 67) or with 131I (n = 38) for diagnostic follow-up. rhTSH, 0.9 mg/d, was injected intramuscularly on 2 consecutive days. Oral diagnostic activities of 5 to 10 mCi (185–370 MBq) 123I or 3 mCi (111 MBq) 131I were given on the third day. DxWBS was performed 24 hours (123I) or 48 to 72 hours (131I) later.
rhTSH-aided 123I DxWBS scans showed 35.3% sensitivity, 98.0% specificity, 85.7% positive predictive value, and 81.6% negative predictive value. rhTSH-stimulated 123I and 131I DxWBS did not differ in scan positivity (10.4% vs. 13.2%, P = 0.75) or disease detection rates (35.3% vs. 27.8%, P = 1.00).
In DTC, rhTSH-aided 123I DxWBS achieves comparable results in diagnostic follow-up with those of rhTSH-aided 131I DxWBS. Future studies should address the preablation setting and scan activity and timing.
From the Departments of *Medicine, †Medical Imaging, and ‡Research Centre, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
Received for publication April 23, 2011; revision accepted June 27, 2011.
Presented (portions of this work) at the 91st Annual Meeting of The Endocrine Society; June 10–13, 2009; Washington, DC.
Conflicts of interest and sources of funding: Editorial assistance on the manuscript was provided by Robert J. Marlowe, Spencer-Fontayne Corporation, Jersey City, NJ. His work was financially supported by Genzyme Corporation, the rhTSH manufacturer. Mr. Marlowe was not involved with the undertaking and writing of this article. All authors have no conflicts of interest.
Reprints: Ali S. Alzahrani, MD, Department of Medicine, MBC-46, King Faisal Specialist Hospital and Research Centre, PO Box 3354, Riyadh 11211, Saudi Arabia. E-mail: aliz@kfshrc.edu.sa.
