Risk factors for radioactive iodine-avid metastatic lymph nodes on post I-131 ablation SPECT/CT in low- or intermediate-risk groups of papillary thyroid cancer

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.

Factors predicting the risk of biochemical incomplete response in well-differentiated thyroid cancer after total thyroidectomy

“…Our study encountered a very high incidence (~29.7%) of lymph nodal metastases on WBS. This finding contrasts with Lee et al, where authors found lymph nodal metastases in 6.5 and 13% of the low and intermediate-risk category patients [28]. In our cohort, overall lymph node metastases were also high.…”

99mTc-Pertechnetate Scintigraphy Predicts Successful Postoperative Ablation in Differentiated Thyroid Carcinoma Patients Treated with Low Radioiodine Activities

“…Then, unfortunately, neither 99m Tc-pertechnetate scintigraphy nor serum Tg would be accurate in detecting lymph node metastases in our series. In contrast, Lee et al [ 12 ] recently found no RAI-avid lymph-node metastases at PT-WBS/SPECT-CT in low-risk DTC patients with rhTSH-sTg values below 0.5 ng/mL. However, their patients were operated on by two experienced thyroid surgeons who performed more than 300 cases of thyroid cancer surgery per year while in Switzerland, due to different reasons, thyroid operations are mostly performed by low-volume general surgeons [ 13 ].…”

Post-Surgical Indications to Radioiodine Treatment and Potential Risk Factors for Post-Treatment Recurrence in Patients with Intermediate-Risk Differentiated Thyroid Carcinoma

“…However, stronger evidence is available concerning RAI employment when specific features of disease are considered. For instance, in a similar population, Lee et al [ 15 ] showed that lymph node metastases reduced recurrence-free survival rates. Seong Young Kwon et al [ 16 ] showed that a high dose of 131 I is necessary to prevent recurrence when more than five nodes are involved.…”