Increased risk of second primary malignancy in thyroid cancer patients treated with radioactive iodine | J Natl Cancer Inst

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Takeaway

  • This study found an increased risk of second primary malignancy (SPM) for thyroid cancer patients treated with radioactive iodine (RAI), especially with cumulative RAI doses over 150 mCi.

Key results

  • Among 20,235 patients with thyroid cancer, 692 cases of SPM were identified.
  • Standardized incidence ratio (SIR) for any SPM was 1.41 (95% confidence interval [CI]=1.31 to 1.52).
  • Higher statistically significantly SIR was seen in leukemia (2.74), non-Hodgkin's lymphoma (2.38), and prostate (2.30), lung and mediastinum (1.93), pancreas (1.83), kidney (1.81), breast (1.48), and colon-rectum (1.31) cancers.
  • Cumulative RAI dose (per 30 mCi increase) conferred a strong risk for SPM (adjusted hazard ratio [aHR]=1.01, 95% CI=1.01 to 1.02, P<.001) and leukemia (aHR=1.03, 95% CI=1.02 to 1.04, P<.001).
  • Cumulative RAI dose 150 mCi possessed a statistically significant risk for all cancer combined (aHR=1.30) and leukem...