Long-term effect of single radioiodine ablation for the remnant thyroid tissue on salivary gland function in patients with differentiated thyroid cancer: Evaluation with Tc-99m pertechnetate scintigraphic changes

Objectives To evaluate long-term effect of radioiodine ablation (RIA) on salivary gland (SG), Tc-99m pertechnetate salivary gland scintigraphy (SGS) was performed at after RIA and imaging findings were compared with those acquired before RIA. The relationship between symptoms and scintigraphic findings were further investigated.

Methods SGS was performed before RIA (Pre-SGS) and at a median follow-up of 53 mo after RIA (F/U SGS) in 171 subjects undergoing RIA after thyroidectomy. All patients had no additional RIA during follow-up. Uptake score (US) and ejection fraction (EF) of each SG in both SGSs were obtained. Compared to Pre-SGS and F/U SGS, significant decreased uptake (Dec-up) was defined when US difference was > 1 and significant decreased EF (Dec-EF) was defined when EF difference was > 20%. Symptoms related with SG dysfunction were evaluated at F/U SGS.

Results Dec-up was observed in 46.8% and Dec-EF in 45.0% in 171 subjects and common in subjects received higher dose of RI (150-200 vs 100 mCi). Both parotid gland dysfunction was frequently observed (52%). Dry mouth was noted in 20.5% at F/U SGS. Dry mouth developed significant higher in subjects received higher dose of RI. Dry mouth was more frequently reported in subjects with Dec-up in submandibular gland than in parotid gland (68.8% vs 33.3%). Dry mouth was correlated with number of the SG with Dec-up.

Conclusions Dec-up and Dec-EF in SG were frequently observed after single RIA. Dry mouth was frequently observed in patients with submandibular gland dysfunction. In an attempt to maximize potential benefit of RAI, minimizing adverse effect in SG is needed

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Relation between dry mouth and number of salivary gland with significant decreased uptake