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Timing between thyroidectomy, radioactive iodine does not affect DTC outcomes
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Disease outcomes in differentiated thyroid cancer, or DTC, are not influenced by the time between total thyroidectomy and radioactive iodine dosing, study data show.
“[Radioactive iodine] therapy is widely used in the management of DTC patients,” the researchers wrote. “However, the impact of the time interval between [total thyroidectomy] and [radioactive iodine] administration on the response to treatment remains a matter of discussion.”
Ana Luiza Maia, MD, PhD, of the thyroid section, endocrine division at the Hospital de Clínicas de Porto Alegre in Brazil, and colleagues evaluated data on 545 adults (mean age at diagnosis, 44.9 years; 80% women) with DTC who attended the thyroid outpatient clinic at the hospital from 2000 to 2015.
According to TNM classification of malignant tumors, 59.1% of participants had stage I disease, 11.4% had stage II, 11.9% had stage III and 15% had stage IV. Among the cohort, 41.8% had a low risk level according to American Thyroid Association classification, 45% had intermediate risk and 13.2% had high risk.
Median time interval between total thyroidectomy and radioactive iodine (RAI) was 6 months. Participants were divided into two groups based on time interval between total thyroidectomy and RAI: less than 6 months after total thyroidectomy (n = 295) or more than 6 months (n = 250). Participants in the more than 6-month group were older (P = .002), had less cervical metastasis (P = .002) and were more commonly classified as low risk by ATA classification (P = .027).
Fifty-nine percent of the less than 6-month group and 65.6% of the more than 6-month group were disease-free 1 year after initial therapy; the rates were similar after a median follow-up of 6 years. No differences existed between the groups for recurrence rates.
Persistent disease was not associated with timing of RAI after further analysis by multiple logistic regression (RR = 0.97; 95% CI, 0.8-1.19).
“We show that the time between [total thyroidectomy] and RAI dosing does not impact disease outcomes (response to initial therapy, disease status on follow-up and recurrence rate) in patients with DTC,” the researchers wrote. “These findings are valid for all ATA risk categories, including high-risk patients and may have some important clinical implications. First, we can reassure the patients that the RAI therapy, whenever indicated, can be safely administered at any time within the first year after thyroid surgery. Most importantly, we show that concerns about early RAI therapy are not justified, and RAI administration may be safely planned according to the logistics of the local health and the patient itself.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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