Salivary gland toxicity after radioiodine therapy for thyroid cancer

Salivary gland toxicity is a common, but not widely appreciated, adverse effect of high-dose radioiodine (131I). This study was carried out to determine the incidence of symptoms of salivary gland damage after 131I treatment for differentiated thyroid cancer.

This was a prospective study of 76 consecutive patients attending thyroid cancer treatment. Symptoms of salivary gland damage (dry mouth, pain and swelling) were assessed during hospital admission and at follow-up visits. Additionally, a retrospective analysis was carried out of patients recorded in our database as having chronic salivary gland swelling after 131I ablation.

Twenty patients (26%) developed salivary gland toxicity, 11 (15%) had symptoms within the first 48 h, continuing for 12 months in seven of these patients. The onset of toxicity in a further nine (12%) patients with persistent symptoms did not occur until 3 months after therapy. In total, 16 (21%) patients had evidence of chronic toxicity, typically xerostomia, at 12 months. Toxicity was more common after repeated 131I administration. After searching our thyroid cancer database, we identified an additional five patients to have chronic salivary gland swelling (chronic sialadenitis or pleomorphic adenoma) 20 months to 23 years after 131I.

Pain, swelling and dry mouth occurred frequently after 131I, with some developing symptoms months or years after administration. Early recognition of salivary gland complications may help to reduce morbidity in these patients.