Graves' orbitopathy development in thyroid cancer patients: a 16-year nationwide cohort study in South Korea.

Background/objectives: We aimed to investigate the prevalence, risk factors, and prognosis of Graves' orbitopathy (GO) in patients with thyroid cancer without a history of hyperthyroidism.

Subjects/methods: This retrospective cohort study analysed a sample from the Korean National Health Insurance Service database, which included 1,137,861 subjects from 2002 through 2019. Patients diagnosed with thyroid cancer, without a history of hyperthyroidism, were identified according to the Korean Standard Classification of Disease codes. The study compared the type of surgery, dose of radioactive iodine (RAI), and daily average thyroid hormone dose between patients who developed GO after being diagnosed with thyroid cancer and those who did not develop GO. We analysed the course of GO and the type of treatment.

Results: A total of 8499 cancer patients without a history of hyperthyroidism were identified, among whom 7836 underwent thyroidectomy. Of those who underwent thyroidectomy, 12 developed GO postoperatively. Among the 663 patients who did not undergo thyroidectomy, none developed GO. The prevalence of GO among thyroid cancer patients was 0.14%. The GO group received a significantly higher total RAI dose than the non-GO group (p = 0.036). There were no significant differences in sex, age, type of surgery, rate of RAI treatment, or average thyroid hormone dose between the two groups. One of the 12 patients who developed GO required intravenous steroids.

Conclusions: Although GO rarely develops in thyroid cancer patients without coexisting hyperthyroidism, the total RAI dose may increase its risk. Further research would help clarify GO's association with thyroid cancer.