Scintigraphic evaluation of salivary gland dysfunction in patients with thyroid cancer after radioiodine treatment.

PURPOSE: Sialadenitis is a well-recognized adverse effect of high-dose radioactive iodine treatment. This study was undertaken to determine whether Tc-99m pertechnetate salivary gland scintigraphy may be used for objective assessment of salivary gland function in patients with thyroid cancer treated with I-131. PATIENTS AND METHODS: The study group consisted of 71 patients (16 men, 55 women) with a mean age of 44 years (range, 16 to 73 years). Twenty-six (37%) patients were not given any radioiodine, and 18, 16, and 11 patients received doses of 100, 150, or 200 mCi (or higher), respectively. Parotid and submandibular glands were evaluated based on a four-grade scoring system. Correlation between the type of surgery, administered dose, time since therapy, subjective symptoms, and findings of salivary gland scintigraphy were evaluated.
RESULTS: Subjective symptoms were questioned in 39 of the 45 patients who received radioactive iodine treatment. Fifty-four percent (21 of 39) of the patients reported xerostomia, of whom 86% (18 of 21) showed salivary gland dysfunction. Objective salivary gland dysfunction was observed in 69% (31 of 45) of patients. In 81% of the patients, the parotid glands were affected; in 13% of the patients, the submandibular glands were affected; and in 6%, both were affected ( < 0.000001). The frequency of salivary gland dysfunction showed a dose dependence to cumulative activity ( = 0.007). A greater complication rate was observed in patients with total thyroidectomy compared with subtotal surgery, although the correlation was not significant ( = 0.625).
CONCLUSIONS: Parenchymal damage to the salivary glands induced by radioactive iodine treatment can be evaluated by salivary gland scintigraphy. The impairment is worse in the parotid glands and increases with the total dose.