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 (131I) 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 131I 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 300νg of selenium orally for 10 days, from 3 days before to 6 days after 131I 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 131I treatment. Serum amylase and whole blood selenium levels were measured before and 2 days and 6 months after 131I 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 131I 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 131I treatment was effective to reduce salivary glands damage by 131I radiation in patients with differentiated thyroid cancer.