Salivary glands ultrasound examination after radioiodine-131 treatment for differentiated thyroid cancer

Background: The most important side effect of radioiodine ( 131 I) therapy is sialoadenitis and xerostomy. Aim: To evaluate by ultrasound (US) parotid and submandibular glands after 131 I therapy for differentiated thyroid cancer (DTC). Patients: Seventy-six subjects thyroidectomized for DTC submitted to salivary glands US examination. Forty-three of them had been previously treated with 131 I: 22 with 1.11 GBq (30 mCi) for remnant ablation, and 21 with higher doses [up to 44.4 GBq (1200 mCi)] for metastases. Thirty-three subjects studied before 131 I therapy served as controls. Parotid and submandibular volume, homogeneity, and echogenicity were determined. 131 I-treated patients filled a questionnaire about sialoadenitis symptoms. Results: Parotid gland volume was significantly higher in treated patients (28.3±16.2 ml) than in untreated patients (20.7±10.4 ml, p=0.0154) and related to the time from last 131 I therapy. Three had parotid volume <1.5 ml and complained severe xerostomy. Submandibular gland volume was similar in treated (11.2±7.6 ml) and untreated patients (8.6±4.2 ml, p=0.0602). Homogeneity and echogenicity were similar in treated and untreated patients. Sialoadenitis symptoms were reported in 26% and were related to the 131 I cumulative dose. Symptoms were not related to gland volume. Hypoechogenicity and inhomogeneity of the parotids were more frequent in patients with salivary stickiness. Conclusion: Parotid, but not submandibular, volume is increased after 131 I treatment depending on the received activity and the time from irradiation but not on sialoadenitis symptoms. Xerostomy is associated to gland atrophy at US.