Postablative 131I SPECT/CT Is Much More Sensitive Than Cervical Ultrasonography for the Detection of Thyroid Remnants in Patients After Total Thyroidectomy for Differentiated Thyroid Cancer

Postablative 131I SPECT/CT Is Much More Sensitive Than Cervical Ultrasonography for the Detection of Thyroid Remnants in Patients After Total Thyroidectomy for Differentiated Thyroid Cancer:



Purpose

Evaluation of utility of cervical ultrasound (US) for detection of thyroid remnants (ThR) in patients after thyroidectomy for differentiated thyroid cancer.

Methods

Included were 154 consecutive patients (17–89 years, 123 female and 31 male patients), without known cancer residues or cervical lymph nodes metastases, admitted for ThR ablation with 131I, 14 to 20 weeks after surgery. Neck uptake of 131I (Tup) and thyroglobulin were determined, and location and volume of ThR detected by cervical US were recorded. On days 3 to 4 after ablation (1.7–4.6GBq, 46–124.3 mCi 131I), neck SPECT/CT was performed, and 131I uptake foci were assigned to one of the regions as described below. The anterior neck was divided into 2 compartments: superior and inferior to lower margin of thyroid cartilage, and each compartment was subdivided into middle and lateral regions (in SPECT/CT, posterolateral and anterolateral regions were also marked out). 131I uptake sites and ThR detected by US, if congruent with SPECT/CT, were counted and analyzed.

Results

In total, 341 131I uptake foci were found in 150 patients (97.4%) by SPECT/CT and 213 corresponding ThR in 118 patients (76.6%) by US. Ultrasound detected 30% to 46% of 131I uptake foci in superior lateral regions, 49% in pyramidal lobe/thyroglossal duct area (both P 0.05). Correlation between ThR volume and Tup was strong (r = 0.79), and that between ThR volume and thyroglobulin was weak (r = 0.24).

Conclusions

Ultrasound is less sensitive than 131I posttherapy scans for ThR detection in patients after thyroidectomy, especially for remnants located above the lower margin of thyroid cartilage.

Received for publication June 21, 2020; revision accepted August 9, 2020.

Work was performed at the Department of Nuclear Medicine and Oncological Endocrinology, Maria Skłodowska-Curie Memorial District Hospital, ul. Parzęczewska 35, 95-100 Zgierz, Poland.

Conflicts of interest and sources of funding: none declared.

Correspondence to: Jacek Makarewicz, MD, PhD, Department of Nuclear Medicine and Oncological Endocrinology, Maria Skłodowska-Curie Memorial District Hospital, ul. Parzęczewska 35, 95-100 Zgierz, Poland. E-mail: jmak@csk.umed.lodz.pl.

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