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Cancer risk after iodine-131 therapy for hyperthyroidism
1Department of Cancer Prevention, Radiumhemmet, Karolinska Hospital, Stockholm, Sweden.
Journal of the National Cancer Institute
|August 7, 1991
Summary
Radioactive iodine (131I) therapy for hyperthyroidism showed a slightly increased overall cancer risk. Lung and kidney cancers were elevated, with stomach cancer risk increasing over time.
Area of Science:
- Endocrinology
- Oncology
- Radiology
Background:
- Hyperthyroidism is commonly treated with radioactive iodine (131I) therapy.
- Long-term cancer risks following 131I therapy require ongoing investigation.
Purpose of the Study:
- To assess cancer incidence in patients treated with 131I for hyperthyroidism.
- To determine if 131I therapy is associated with increased cancer risk over time.
Main Methods:
- A cohort of 10,552 hyperthyroid patients treated with 131I between 1950-1975 was studied.
- Cancer incidence was tracked via linkage with the Swedish Cancer Register (1958-1985).
- Standardized incidence ratios (SIR) were calculated to compare observed vs. expected cancer rates.
Main Results:
- Overall cancer incidence was slightly elevated (SIR = 1.06).
- Significantly increased risks were observed for lung (SIR = 1.32) and kidney cancers (SIR = 1.39).
- Among 10-year survivors, elevated risks for stomach, kidney, and brain cancers were noted. Stomach cancer risk increased with time and administered activity.
Conclusions:
- 131I therapy for hyperthyroidism is associated with a small increase in overall cancer risk.
- Specific cancer types, including lung, kidney, and stomach, showed elevated risks.
- The findings suggest a potential link between 131I and certain radiogenic cancers, particularly stomach cancer.