Clinical Thyroidology® for the Public
Summaries for the Public from recent articles in Clinical Thyroidology
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HYPERTHYROIDISM
Cancer risk following radioiodine treatment of hyperthyroidism
BACKGROUND
Radioactive iodine plays a valuable role in diagnosing and treating thyroid problems as it is taken up only by thyroid cells. There are 2 forms of radioactive iodine: one does not damage the thyroid cells and is used to take pictures of the thyroid (I-123) and the other (radioactive iodine therapy) is the destructive form used to destroy thyroid tissue in the treatment of thyroid cancer or an overactive (hyperthyroid) thyroid (I-131). Radioactive iodine therapy is a mainstay in treating patients with thyroid cancer. While radioactive iodine therapy is an effective treatment for hyperthyroidism, additional therapies are available including antithyroid medications and surgery. Treatment decisions consider the risks and benefits associated with each option. In recent years, there has been an increased concern regarding the risk of radioactive iodine therapy in hyperthyroidism since there are alternative treatments.
Conflicting data has been published in the literature regarding whether radioactive iodine therapy for hyperthyroidism is associated with an increased risk of developing cancer. This study sought to determine the cancer risk following treatment with radioactive iodine therapy for hyperthyroidism. Specifically, the authors examined the risk of cancer development and death after radioactive iodine therapy exposure.
THE FULL ARTICLE TITLE
Shim SR et al 2021 Cancer risk after radioactive iodine treatment for hyperthyroidism: A systematic review and meta-analysis. JAMA Netw Open 4:e2125072. PMID: 34533571.
SUMMARY OF THE STUDY
This study included results from 12 studies with a total of 479,452 study participants. Studies were included in the analysis if they met the following criteria: included patients treated for hyperthyroidism with radioactive iodine therapy and followed until cancer diagnosis or death and included at least one comparison patient group not treated with radioactive iodine therapy.
Results of this analysis indicated that no significant differences in overall cancer risk between patients treated with radioactive iodine therapy. There was no increased risk for any specific cancer except thyroid cancer, which showed a slight increased risk in patients treated with radioactive iodine therapy. They also observed a significant correlation between radioactive iodine therapy dose and increased risk of breast and solid cancer death in a small subset of studies. Overall, the data were reassuring and suggest that the potential increased risk of cancer following radioactive iodine therapy treatment is small and only associated with higher doses of radioactive iodine.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This data shows that there overall no increased risk of cancer after treating patients with hyperthyroidism with radioactive iodine therapy. This study provides general reassurance to the patient and doctor. However, there may be some increased risk following high doses of radioactive iodine therapy and further research is needed in this area. Careful discussion of the risks and benefits of each treatment option are important to determine the best hyperthyroid treatment for the individual patient.
— Whitney Woodmansee MD
ATA THYROID BROCHURE LINKS
Radioactive Iodine Therapy: https://www.thyroid.org/radioactive-iodine/
Hyperthyroidism (Overactive): https://www.thyroid.org/hyperthyroidism/
Graves’ Disease: https://www.thyroid.org/graves-disease/
ABBREVIATIONS & DEFINITIONS
Radioactive iodine (RAI): this plays a valuable role in diagnosing and treating thyroid problems since it is taken up only by the thyroid gland. I-131 is the destructive form used to destroy thyroid tissue in the treatment of thyroid cancer and with an overactive thyroid. I-123 is the nondestructive form that does not damage the thyroid and is used in scans to take pictures of the thyroid (Thyroid Scan) or to take pictures of the whole body to look for thyroid cancer (Whole Body Scan).
Hyperthyroidism: a condition where the thyroid gland is overactive and produces too much thyroid hormone. Hyperthyroidism may be treated with antithyroid meds (Methimazole, Propylthiouracil), radioactive iodine or surgery.
Graves’ disease: the most common cause of hyperthyroidism in the United States. It is caused by antibodies that attack the thyroid and turn it on.
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