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RAI Therapy and the Risk of Undiagnosed Thyroid Cancer

© Keri

As we have discussed before, preferred treatment for hyperthyroidism differs in Europe and North America. Many European physicians prefer the surgical removal of the thyroid over treatment with I131. They consider microscopic examination of the thyroid as essential in the diagnosis of potential causes of hyperthyroidism, including rare thyroid tumors that are associated with increased thyroid production.

To help evaluate whether RAI was a risk factor in the missed diagnosis of thyroid cancer, a recent study published in the Journal of Nuclear Medicine looked at data collected from 6647 patients treated for hyperthyroidism from 1970 to 1997 in Italy. All were treated with RAI. Seventy-six percent of the patients had an autonomously functioning node or toxic multinodular goiter. The others had Graves' disease. Sixty percent were over 60 years old.

The data review showed that after treatment, thyroid cancer was discovered in 10 (0.15%) patients with nodes or nodules and none in the group with Graves' disease. Five of the patients had been treated before the use of ultrasound as a diagnostic tool. Overall the study found that the incidence of thyroid cancer in patients treated with radioiodine to be 150 out of 100,000 over a 27-year period compared with 124.88 out of 100,000 in the general population.

The researchers concluded that "accurate preliminary evaluation (clinical examination, sonography, and cytologic evaluation of fine-needle aspiration) is fundamental for a proper choice between radioiodine and surgical therapy." In other words, the choice of RAI vs. surgery should be based on the findings of a complete workup of any lumps or goiter. Interestingly, there were no findings of thyroid cancer in the group with Graves' disease.

Source:

Angusti T Codegone A Pelerito R Favero A. Thyroid cancer prevalence after radioiodine treatment of hyperthyroidism J Nucl Med 2000 Jun;41(6):1006-9 accessed through the National Library of Medicine:

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