Hyperthyroidism: radioiodine tied to excess risk for cancer death

  • Kitahara CM & al.
  • JAMA Intern Med
  • 1 Jul 2019

  • International Clinical Digest
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Takeaway

  • Radioactive iodine (RAI) treatment is associated with excess risk for death from solid cancer in patients with hyperthyroidism.

Why this matters

  • RAI is commonly used for hyperthyroidism treatment and is widely considered to be safe and effective.
  • Organ-absorbed doses are positively associated with solid cancer mortality.

Key results

  • Malignancy was the primary cause of death in 15.3% of patients.
  • RAI was associated with all solid cancer mortality (relative risk [RR], 1.06; P=.002 for 100-mGy dose to the stomach).
    • Breast cancer: RR, 1.12; P=.04 for 100-Gy dose to the breast.
    • All other solid cancers combined: RR, 1.05; P=.01 for 100-Gy dose to the stomach.
  • For patients receiving typical RAI doses (150-250 mGy) to the stomach, lifetime excess solid cancer deaths were estimated as 19-32 per 1000 patients treated at age 40 years and 18-31 per 1000 patients treated at age 50 years.

Study design

  • 18,805 patients with hyperthyroidism treated with RAI with no history of cancer were included.
  • This study is a 24-year extension of the multicenter Cooperative Thyrotoxicosis Therapy Follow-up Study.
  • Funding: Intramural Research Program of the National Cancer Institute, NIH.

Limitations

  • Uncertainties in organ dose estimations.
  • Limited statistical power for many cancers of interest.
  • Results unadjusted for smoking, obesity, alcohol use, or reproductive factors.