Dear Editor,

The analysis published by Kithara and colleagues regarding the association of radio-iodine exposure and later risk of cancer is of great importance and should impact the way we use this treatment in patients with hyperthyroidism [1]. Their cohort consisted of 18,805 patients with a mean age of 49 years at entry. The majority of patients included in the analysis (94%) received radio-iodine for Graves’ disease. Authors calculated a lifetime excess of solid cancer deaths of 12 (95% confidence interval 2–26) to 31 (95% confidence interval 5–64) per 1000 patients treated at age of 50, respectively. Graves’ disease is a condition that can also be treated by antithyroid drugs. However, this therapy has a relapse rate of around 30–60% depending on individual patients’ factors [2].

The 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism recommend that patients with overt Graves’ hyperthyroidism should be treated with any of the following modalities including radio-iodine, antithyroid drugs, or surgery [2]. These guidelines also state that there is not enough evidence to assume a relevant cancer risk after radioactive iodine treatment [2], a statement that now needs revision given the new evidence presented [1]. When counseling patients regarding the best first-line treatment for Graves’ disease, physicians should use a shared decision making approach outlining the risks and benefits of each treatment option and providing estimates regarding recurrence risks with antithyroid drug therapy based on recently published clinical scores (i.e., GREAT score) [3, 4].