Issue: May 2015
April 15, 2015
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RAI treatment may increase second primary malignancy risk among children, young adults with thyroid cancer

Issue: May 2015
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An elevated risk for second primary malignancy, especially salivary gland cancer, was found among pediatric and young adult patients who received radioactive iodine for differentiated thyroid cancer, according to recent study findings published in Thyroid.

“The use of adjuvant radioactive iodine therapy in patients with thyroid cancer is known to be associated with an escalated risk of second primary malignancies,” the researchers wrote. “This risk has been quantified in several large studies of adult patients. Risks have not been well defined in the pediatric population, due to the relative rarity of this cancer in this population.”

Luc G. T. Morris, MD, MSc, FACS, of Memorial Sloan Kettering Cancer Center in New York, and colleagues evaluated 3,850 pediatric and young adult patients (< 25 years) from the SEER 17 Registry between 1973 and 2008 undergoing treatment with surgery and with or without radioactive iodine (RAI) for differentiated thyroid cancer (DTC) to determine the risk for second primary malignancies attributable to RAI among this population.

Overall, 43.6% of patients received postoperative RAI. The number of patients receiving postoperative RAI increased from 4% in 1973 to 62% in 2008 (P < .001).

Patients treated with RAI developed excess second primary cancers, mostly salivary cancers and smaller numbers of leukemias and renal cancers. No increased risk for second primary malignancy was found among the group not treated with RAI.

“It is critical to carefully weigh the risks and benefits of RAI therapy in young patients,” the researchers wrote. “This is a decision that needs to be considered in light of both patient and tumor characteristics on a case-by-case basis. In young patients with distant metastases or high-volume, extensive nodal mestastases, that are likely to be iodine-avid, the benefits of RAI therapy probably outweigh the risks of [second primary malignancies] we have described. However, in many cases, such as patients with intrathyroidal, node-negative tumors, or patients with low-volume central compartment nodal micromestastases, who have an excellent long-term prognosis and low risk of locoregional recurrence, the risks of developing [second primary malignancies] may outweigh the minimal benefits of RAI therapy.” – by Amber Cox

Disclosure: The researchers report no relevant financial disclosures.