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Comment & Response
December 2019

Safety of the Use of Radioactive Iodine in Patients With Hyperthyroidism—Reply

Author Affiliations
  • 1Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
  • 2Hirosoft International, Eureka, California
JAMA Intern Med. 2019;179(12):1739. doi:10.1001/jamainternmed.2019.5123

In Reply We appreciate the opportunity to respond to the letters from Peacock and colleagues and Grady and colleagues regarding our Original Investigation.1 The aim of our study was to investigate the dose-response relationship between estimated organ doses and cancer mortality risks in patients treated with radioactive iodine (RAI) for hyperthyroidism. This was the major strength of our study compared with earlier analyses of this and other cohorts, which relied on the cruder approach of comparing risks in exposed and unexposed patients. Dose-response relationships are less likely to be explained by confounding and, thus, provide stronger evidence in support of a causal relationship.2 These estimates also quantify the risk per unit dose, which can be translated into estimated absolute risks. In the article,1 we emphasized that the magnitude of the risk associated with current typical treatment doses is small (20-30 lifetime excess cancer deaths per 1000 patients treated with RAI).

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