Abstract
ObjectivePost I-131 ablation single-photon emission computed tomography (SPECT)/CT can show radioactive iodine (RAI)-avid cervical metastatic lymph nodes (mLN) in differentiated thyroid cancer. This study aimed to evaluate the incidence of RAI-avid mLN on post I-131 ablation SPECT/CT and the risk factors related to metastasis among patients with papillary thyroid cancer (PTC) in the low- or intermediate-risk groups.Study design and settingAmong 339 patients with PTC who underwent total thyroidectomy followed by I-131 ablation, 292 (228 women, 64 men) belonging to the low- or intermediate-risk groups before I-131 ablation, and with sufficient clinical follow-up data were enrolled. The risk groups were classified based on the American Thyroid Association 2015 guideline. Each patient was followed-up for at least 24 months after the ablation (median: 30 months). The clinical, pathologic, and biochemical factors of PTC were reviewed, and their relationships to RAI-avid mLN on SPECT/CT were analyzed.ResultsOf the 292 patients, 61 and 231 belonged to the low-and intermediate-risk groups, respectively. Four (6.5%) patients in the low-risk group and 31 (13.0%) patients in the intermediate-risk group had RAI-avid mLN. A high preablation TSH-stimulated serum thyroglobulin (Tg) level in the low- or intermediate-risk group predicted the presence of RAI-avid mLN (cut-off = 0.5; hazard ratio (HR): 2.96; p = 0.04). In the subgroup analysis by risk group, TSH-stimulated serum Tg only predicted RAI-avid mLN in the low-risk group (cut-off = 1.0; HR: 5.3; p = 0.03).ConclusionThe incidence of RAI-avid mLN on postablation SPECT/CT was relatively high in both low- and intermediate-risk patients with PTC, and high preablation TSH-stimulated serum Tg level was a predictor of metastasis, especially in the low-risk group. A selective treatment approach should be considered in patients with high preablation TSH-stimulated serum Tg level.
Highlights
Residual normal or malignant thyroid tissue after total thyroidectomy for differentiated thyroid carcinoma (DTC) is a common finding
The incidence of Radioactive iodine (RAI)-avid metastatic lymph nodes (mLN) on postablation single-photon emission computed tomography (SPECT)/CT was relatively high in both lowand intermediate-risk patients with papillary thyroid cancer (PTC), and high preablation TSH-stimulated serum Tg level was a predictor of metastasis, especially in the low-risk group
The current study aimed to evaluate the incidence of hidden RAI-avid mLN on RxSPECT/ CT after curative surgery in patients with PTC belonging to the low- or intermediate-risk groups according to the 2015 American Thyroid Association (ATA) guideline, and to investigate the risk factors related to the occurrence of metastasis
Summary
Residual normal or malignant thyroid tissue after total thyroidectomy for differentiated thyroid carcinoma (DTC) is a common finding. Radioactive iodine (RAI) can be administered to thyroidectomized patients for remnant ablation or as an adjuvant therapy. Some retrospective studies have shown that RAI treatment improves the survival rate and decreases the recurrence rate of papillary thyroid cancer (PTC) [1, 2]. The 2015 American Thyroid Association (ATA) Management Guidelines for DTC do not recommend routine RAI remnant ablation for low-risk DTC patients [3]. The incidence of residual lymph node (LN) metastasis after total thyroidectomy is relatively high even in DTC patients with small intrathyroidal tumors [4].
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