Nasolacrimal duct obstruction as a complication of iodine-131 therapy in patients with thyroid cancer.
PURPOSE
There are few studies evaluating the effect of radioioine therapy on the lacrimal drainage system. This study reports on symptomatic and asymptomatic nasolacrimal duct obstruction (NLDO) as complications of high-dose radioiodine therapy in these patients.


METHODS
Eighty-one cases were randomly selected from a population of radioiodine-treated differentiated thyroid carcinoma patients and were enrolled in a historical cohort study. The patients were categorized into four subgroups on the basis of the received cumulative dose of iodine-131 (I-131). In addition, 17 age-matched and sex-matched individuals were selected as the control group. Using dacryoscintigraphy and a clinical datasheet, the patients and controls were evaluated for partial or complete and symptomatic or asymptomatic NLDO. The data on different subgroups of patients were compared with the data of the control group.


RESULTS
Twenty-nine out of 162 exposed eyes (18%) and three out of 34 control eyes (9%) had evidence of NLDO on scintigraphic images. Among patients treated with less than 11.1 GBq of I-131 (subgroup A), six out of 78 eyes (7.7%) had partial or complete NLDO. This was evident in 23 out of 84 eyes (27.4%) among patients treated with 11.1 GBq or more (subgroup B). The frequency of complete NLDO increases significantly when the cumulative dose of radioiodine exceeds 11.1 GBq (2.9% in the control group, 3.8% in subgroup A, and 23.8% in subgroup B; P=0.006).


CONCLUSION
NLDO may be considered as a side effect of I-131 therapy, especially with a cumulative dose of 11.1 GBq or more.