Increased cancer incidence after radioiodine treatment for hyperthyroidism

Cancer. 2007 May 15;109(10):1972-9. doi: 10.1002/cncr.22635.


Background: Concerns remain about risk of cancer after radioactive iodine (RAI) treatment for hyperthyroidism, especially in organs that concentrate iodine. The objective was to assess the long-term cancer risk from RAI treatment for hyperthyroidism.

Methods: A total of 2793 hyperthyroid patients treated with RAI at Tampere University Hospital between 1965 and 2002, and 2793 age- and sex-matched reference subjects were followed for an average of 10 years through the Finnish Cancer Registry.

Results: Cancer incidence among hyperthyroid patients treated with RAI was higher than in the population-based control group (118.9 vs 94.9 per 10,000 person-years, rate ratio [RR], 1.25; 95% confidence interval [CI]: 1.08-1.46). Furthermore, incidence of stomach (RR, 1.75, 95% CI: 1.00-3.14), kidney (RR, 2.32; 95% CI: 1.06-5.09), and breast (RR, 1.53; 95% CI: 1.07-2.19) cancer was increased among RAI-treated patients. The relative risk of cancer increased with higher RAI dose administered. The increase in cancer incidence was statistically significant in patients treated at the age of 50-59 (RR, 1.44; 95% CI: 1.05-1.97) or older than 70 years (RR, 1.39; 95% CI: 1.05-1.82). There was a 5-year latent period after the RAI treatment before the cancer incidence began to differ between the RAI-treated hyperthyroid patients and the control group.

Conclusions: Cancer incidence, especially cancer of the stomach, kidney, and breast, was higher in patients treated with RAI for hyperthyroidism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Female
  • Finland / epidemiology
  • Follow-Up Studies
  • Humans
  • Hyperthyroidism / radiotherapy*
  • Incidence
  • Iodine Radioisotopes / adverse effects*
  • Iodine Radioisotopes / therapeutic use
  • Male
  • Middle Aged
  • Neoplasm Recurrence, Local
  • Neoplasms, Radiation-Induced / epidemiology
  • Neoplasms, Radiation-Induced / etiology*
  • Radiotherapy Dosage
  • Risk Factors


  • Iodine Radioisotopes