Clinical significance of extra-thyroid ^99mTc-pertechnetate uptake before initial radioiodine therapy for...

To analyse the clinical characteristics of extra-thyroid ^99mTc-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.

This study retrospectively selected patients with DTC and extra-thyroid ^99mTc-pertechnetate uptake. The clinical features, location, location count and extra-thyroid ^99mTc-pertechnetate uptake distribution were analysed, combined with the uptake rate, stimulated thyroglobulin (sTg) level, post-therapy whole-body scan and curative effect.

A total of 38 patients were enrolled in the study and 65 extra-thyroid ^99mTc-pertechnetate foci were detected. Thirty-four patients showed abnormal ^99mTc-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). ¹³¹I uptake was found in 36 patients at the ^99mTc-pertechnetate uptake site. The number of iodine uptake foci was significantly higher than that of ^99mTc-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).

Extra-thyroid ^99mTc-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.