Endocrine Abstracts

Radioiodine (¹³¹I, RAI) has traditionally been used in thyroid cancer treatment but its benefitshould be balanced against possible risks. Among them, salivary gland dysfunction has oftenbeen discussed, although the reported data have been inconsistent. While some authors reported functional changes following higher (mostly cumulative) activities, there have been scarce data on the activity of 3.7 GBq (100 mCi) that is most commonly used for RAI remnant ablation (RRA). The aim of our prospective study was to evaluate salivary gland function in 31 thyroidectomised patients (6 men, 25 women; median age, 52 years) before and 4 to 6 months after RRA, using 3.7 GBq¹³¹I-NaI. Salivary gland uptake (reflecting parenchymal integrity) and excretion fraction (reflecting secretory function) werequantitatively assessed with ^99mTc – pertechnetate salivary gland scintigraphy. Pre – and posttreatment values were compared using Wilcoxon signed rank test. No significant difference was observed in parotid (median absolute change, +0.01%; 95% confidence interval, –0.02 to +0.03%) or submandibular (0.00%; –0.02 to +0.02%) glands uptake, as well as in parotid (+0.4%; –4.6 to +6.1%) or submandibular (+3.2%; –1.0 to +8.4%) excretion fraction (absolute values in Table). The calculated power for minimum relevant (relative) difference of 25% and sample size of 31 ranged between 86 and 96% for the individual variables, making our negative results reasonably reliable. They suggest that RRA with the most commonly used ablation activity of 3.7 GBq has no important impact on salivary gland function. Therefore, the concerns about putative salivary gland functional deterioration following RRA are probably unjustified.

Values are expressed as median (interquartile range), P values from Wilcoxon signed rank test.

This work was supported by the programme PROGRES Q40–14.