Long-Term Effects of Radioiodine Treatment on Salivary Gland Function in Adult Survivors of Pediatric Differentiated Thyroid Carcinoma

Pediatric differentiated thyroid cancer (DTC) is a rare disease. Initial treatment of DTC consists of a total or near-total thyroidectomy and131I therapy. Previous studies on adults showed that131I treatment may reduce salivary gland function (SGF). Studies regarding SGF in children treated for DTC are sparse. Our aim was to assess the long-term effects of131I treatment on SGF in survivors of pediatric DTC. Methods: In a nationwide cross-sectional study, SGF in patients treated for pediatric DTC between 1970 and 2013 (.5 y after diagnosis, $18 y old at the time of evaluation) was studied. SGF was assessed by sialometry, sialochemistry, and a xerostomia inventory. Salivary gland dysfunction (SGD) was defined as an unstimulated whole saliva flow of no more than 0.2 mL/min or a stimulated whole saliva flow of no more than 0.7 mL/min. Results: Sixty-five patients underwent131I treatment (median age at evaluation, 33 y, with an interquartile range [IQR] of 25–40 y; 86.2% female; median follow-up period, 11 y, with an IQR of 6–22 y). Median cumulative131I activity was 5.88 GBq, with an IQR of 2.92–12.95 GBq, and 47.7% underwent multiple131I administrations. SGD was present in 30 (47.6%) patients. Levels of amylase and total protein in saliva were reduced. Moderate to severe xerostomia was present in 22 (35.5%) patients. Stimulated salivary secretion was lower and the severity of xerostomia complaints higher in patients treated with higher cumulative131I activity. Conclusion: In survivors of pediatric DTC, clinically significant SGD was found in 35.5% and was related to the cumulative131I activity of the treatment.