Diagnostic value of recombinant human thyrotropin-stimulated ¹²³I whole-body scintigraphy in the follow-up of patients with differentiated thyroid cancer.
OBJECTIVE
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.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Department of Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. aliz@kfshrc.edu.sa
Ali S
AS
Alzahrani
OmAlkhaire
O
AlShaikh
Mahmoud
M
Tuli
Abdulaziz
A
Al-Sugair
Reem
R
Alamawi
Maha M
MM
Al-Rasheed
D014408:Biomarkers, Tumor / Q000097:blood; D001706:Biopsy; D016009:Chi-Square Distribution; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging; D018365:Neoplasm, Residual / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011994:Recombinant Proteins; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin; D013954:Thyroglobulin