Effect of selenium supplementation for protection of salivary glands from iodine-131 radiation damage in patients with differentiated thyroid cancer.

OBJECTIVE: In the current study, we examined whether selenium supplementation during iodine-131 ((131)I) treatment had a radio-protective effect on salivary glands. SUBJECTS AND METHODS: Sixteen patients with differentiated thyroid cancer were prospectively enrolled in the study. Patients after total thyroidectomy, before (131)I treatment, were divided into two groups; 8 patients in the selenium group and 8 patients in the control group. Patients in the selenium group received 300nug of selenium orally for 10 days, from 3 days before to 6 days after (131)I treatment. The control group received a placebo over the same period. To assess salivary gland function, salivary gland scintigraphy was performed before and 6 months after (131)I treatment. Serum amylase and whole blood selenium levels were measured before and 2 days and 6 months after (131)I treatment. Using salivary gland scintigraphy, maximum uptake ratio (MUR), maximum secretion percentage (MSP), and ejection fraction (EF) of each salivary gland were calculated. RESULTS: Baseline clinical characteristics, baseline amylase and selenium levels, and parameters of baseline salivary gland scintigraphy were not significantly different between selenium and control groups (P>0.05). On a blood test performed 2 days after (131)I treatment, the selenium group showed a significantly higher whole blood selenium level (P=0.008) and significantly lower serum amylase level (P=0.009) than the control group. On follow-up salivary gland scintigraphy, the control group showed significantly decreased, MUR of the bilateral parotid and left submandibular glands, MSP of the bilateral parotid and submandibular glands, and EF of the left submandibular glands (P<0.05), while the selenium group only had a significant decrease in MSP of the right submandibular gland and EF of the left submandibular gland (P<0.05). CONCLUSION: Selenium supplementation during (131)I treatment was effective to reduce salivary glands damage by (131)I radiation in patients with differentiated thyroid cancer.