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Radioactive iodine therapy decreases 5-, 10-year mortality rates in differentiated thyroid carcinoma

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May 15, 2017

Treatment with radioactive iodine for differentiated thyroid carcinoma after primary surgical treatment was more effective for decreasing 5- and 10-year mortality than no radiation therapy or external beam radiation, published findings indicate.

Vikas Mehta, MD, MPH, FACS, of the department of otolaryngology – head and neck surgery at Louisiana State University in Shreveport, and colleagues evaluated data from the National Cancer Database on 11,832 adults (mean age, 61.6 years; 57.5% women) with stage IV differentiated thyroid carcinoma who underwent primary surgical treatment between 2002 and 2012 to determine survival among participants who received radioactive iodine (RAI), external beam radiation or neither therapy after surgery.

Overall, 8.76% of participants had follicular thyroid carcinoma (FTC), and 91.24% had papillary thyroid carcinoma (PTC).

Among participants with FTC, the most common cancer stage was stage IV-C (no radiation therapy, 47.6%; external beam radiation therapy, 64.6%; RAI, 53.5%) followed by stage IV-A (no radiation therapy, 39.5%; external beam radiation therapy, 23.1%; RAI, 39.2%) and stage IV-B (no radiation therapy, 12.9%; external beam radiation therapy, 12.3%; RAI, 7.2%). The highest mortality rate was found among participants treated with external beam radiation therapy (5-year mortality, 51.4%; 10-year mortality, 59.9%) compared with no radiation therapy (5-year mortality, 45.5%; 10-year mortality, 51%) and RAI (5-year mortality, 29.2%; 10-year mortality, 36.8%).

Among participants with PTC, the most common cancer stage was stage IV-A (no radiation therapy, 81.5%; external beam radiation therapy, 51.2%; RAI, 86.7%), followed by stage IV-C (no radiation therapy, 12%; external beam radiation therapy, 31.5%; RAI, 9.7%) and stage IV-B (no radiation therapy, 6.5%; external beam radiation therapy, 17.4%; RAI, 3.6%). The highest mortality rate was found among participants treated with external beam radiation therapy (5-year mortality, 46.6%; 10-year mortality, 50.7%) compared with no radiation therapy (5-year mortality, 22.7%; 10-year mortality, 25.5%) and RAI (5-year mortality, 11%; 10-year mortality, 14%).

“RAI was associated with improved 5- and 10-year survival for stages IV-A, IV-B and IV-C PTC and FTC,” the researchers wrote. “In contrast, [external beam radiation therapy] was associated with poorer survival outcomes, particularly with PTC. While indications for treatment with RAI and [external beam radiation therapy] may explain survival differences, the data suggest that treatment with RAI inherently confers better prognosis and survival and treatment with [external beam radiation therapy] confers poorer prognosis and survival.” – by Amber Cox

Disclosure: The researchers report no relevant financial disclosures.