Abstract
We investigated whether an indication for [18F]FDG-PET/CT to detect FDG-avid persistent disease (PD) could be identified precisely using the extent of metastatic lymph nodes (MLNs) and serum thyroglobulin (Tg) in papillary thyroid cancer (PTC) patients. This retrospective study included 429 PTC patients who underwent surgery and radioactive iodine (RAI) therapy. [18F]FDG-PET/CT and serum Tg were evaluated just before RAI therapy. The MLN ratio (LNR) was defined as the ratio of the number of MLNs to the number of removed LNs. To derive the LNR-combined criteria, different Tg cut-off values for identifying the PET/CT-indicated group for PD detection were applied individually to subgroups initially classified based on LNR cut-off values. The cut-off values for serum Tg, the number of MLNs, and LNR for a PET/CT indication were 6.0 ng/mL, 5, and 0.51, respectively. Compared to a single parameter (serum Tg, total number of MLNs, and LNR), the LNR-combined criteria showed significantly superior diagnostic performance in detecting FDG-avid PD (p < 0.001). The diagnostic performance of PET/CT in detecting FDG-avid PD was significantly improved when the PET/CT-indicated group was identified through the LNR-combined criteria in a stepwise manner; this can contribute to a customized PET/CT indication in PTC patients.
Highlights
Well-differentiated thyroid carcinoma (DTC) is the most common thyroid malignancy and generally has an excellent prognosis and a low mortality rate [1,2]
We investigated whether an indication for [18F]FDG-positron emission tomography/computed tomography (PET/CT) to detect FDG-avid persistent disease (PD) could be derived more precisely using the extent of metastatic lymph nodes (MLNs) and serum Tg, and whether the diagnostic performance of PET/CT could be improved by combining the extent of MLNs and serum Tg in patients with papillary thyroid cancer (PTC)
We investigated whether the diagnostic performance of [18F]FDG-PET/CT to detect FDG-avid PD was improved when the PET/CT-indicated group was identified using the LNR-combined criteria compared that using a single parameter
Summary
Well-differentiated thyroid carcinoma (DTC) is the most common thyroid malignancy and generally has an excellent prognosis and a low mortality rate [1,2]. 3–10% patients could have persistent or recurrent disease (PRD) within the first decade after surgery and radioactive iodine (RAI) therapy [3]. Compared to recurrent disease (RD), persistent disease (PD) has different characteristics and requires a different management approach; the corresponding disease definitions and timelines have not been defined clearly. In patients with PD, therapeutic response to RAI therapy is often poor, and life expectancy could be significantly reduced [4]. Bates et al [5] reported that multiple reoperations in patients with DTC were performed for the management of PD and not for the management of RD.
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