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Clin Nucl Med. 2019 Jan;44(1):11-20. doi: 10.1097/RLU.0000000000002321.

Differentiated Thyroid Cancer Outcomes After Surgery and Activity-Adjusted 131I Theragnostics.

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University of Michigan Medical School.
Division of Metabolism Endocrinology and Diabetes, Department of Internal Medicine, and.
Division of Endocrine Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI.



The aim of this study was to determine clinical outcomes in patients with differentiated thyroid cancer after surgery and activity-adjusted I therapy informed by diagnostic I scans with SPECT/CT (Dx scan).


Single-institution retrospective cohort study analysis of clinical outcomes after 1 to 5 years (mean, 39.6 ± 23.4 months) of follow-up in 350 patients with differentiated thyroid cancer associated with histopathologic risk factors, nodal metastases, and/or distant metastases. Postoperatively, all patients underwent Dx scans for completion of staging and risk stratification, and I therapy was based on integration of information from histopathology, stimulated thyroglobulin and scintigraphy.


Twenty-three patients (6.6%) underwent reoperative neck dissection for removal of unsuspected residual nodal metastases identified on Dx scans. Clinical outcomes were as follows: 84.3% complete response, 1.4% biochemical incomplete response, 2.3% indeterminate response, and 12% structural incomplete response. Of the entire cohort, only 8 patients (2.3%) had persistent iodine-avid metastatic disease, which required repeated I therapy. Of 31 patients with iodine-avid distant metastases identified on Dx scans, 13 patients (42%) achieved complete response with a single I treatment.


Detection of regional and distant metastases on postoperative Dx scans permits adjustment of prescribed I activity for targeted treatment, as compared with fixed-activity ablation. This approach resulted in complete response after a single I treatment in 88% patients with histopathologic risk factors and regional metastases and 42% patients with distant metastases. Most patients with structural incomplete response (81%) had elevated thyroglobulin levels with negative follow-up I scans and positive PET/CT and/or CT scans consistent with altered tumor biology (non-iodine-avid disease).

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