Clinical significance of extra-thyroid (99m)Tc-pertechnetate uptake before initial radioiodine therapy for differentiated thyroid carcinoma

OBJECTIVE: To analyse the clinical characteristics of extra-thyroid (99m)Tc-pertechnetate uptake in order to explore the effect of the phenomenon on radioactive iodine (RAI) therapy for differentiated thyroid carcinoma (DTC) and its clinical significance. METHODS: This study retrospectively selected patients with DTC and extra-thyroid (99m)Tc-pertechnetate uptake. The clinical features, location, location count and extra-thyroid (99m)Tc-pertechnetate uptake distribution were analysed, combined with the uptake rate, stimulated thyroglobulin (sTg) level, post-therapy whole-body scan and curative effect. RESULTS: A total of 38 patients were enrolled in the study and 65 extra-thyroid (99m)Tc-pertechnetate foci were detected. Thirty-four patients showed abnormal (99m)Tc-pertechnetate uptake in the lymph nodes (26 of 38; 68.4%), lungs (four of 38; 10.5%) and bones (four of 38; 10.5%). The corresponding uptake rates were 0.2%, 0.2% and 0.8%, respectively. The uptake rate and sTg were significantly positively correlated (r = 0.36). (131)I uptake was found in 36 patients at the (99m)Tc-pertechnetate uptake site. The number of iodine uptake foci was significantly higher than that of (99m)Tc-pertechnetate uptake foci. The sTg value and pathological staging significantly differed between the excellent and nonexcellent response groups (Z = –2.947 and Z = –2.348, respectively). CONCLUSION: Extra-thyroid (99m)Tc-pertechnetate uptake mostly indicated metastases with specific clinical features, which may have prognostic value for the judgment of iodine uptake function and the RAI therapy plan.