Progressive changes in the major salivary gland after radioiodine therapy for differentiated thyroid cancer: a single-center retrospective ultrasound cohort study.

This study aimed to determine the prevalence of radioiodine-induced salivary gland damage by evaluating progressive changes in salivary glands using ultrasound. Four hundred forty-six patients with differentiated thyroid carcinoma who underwent total or near-total thyroidectomy and postoperative radioiodine therapy were retrospectively reviewed. From the first to the fifth follow-up visits, the positive rate of major salivary gland changes on ultrasound gradually increased from 2.0% to 33.0% (P<0.001) and possibly stabilized at the fifth visit (approximately 36 months). The first positive result was detected at an average of 20.78±8.72 months. Only 21 of the 161 positive cases eventually achieved negative ultrasound results (Fisher's test, P<0.001), and the 21 cases simply showed a coarse echotexure. In conclusion, ultrasound changes appeared late, and most of these changes were not reversed.