Patients with intermediate- or high-risk papillary thyroid carcinoma saw no increased overall or disease-free survival benefit when undergoing early vs. delayed radioactive iodine therapy after thyroidectomy, according to findings published in Clinical Endocrinology.
“The time of initiating the first post-thyroidectomy [radioactive iodine] varies worldwide and may be affected by personal, social environmental and disease-related factors,” Bo Hyun Kim, MD, PhD, of the division of endocrinology and metabolism at Pusan National University Hospital in Busan, South Korea, and colleagues wrote in the study background. “The impact of early and late [radioactive iodine therapy] after thyroidectomy on clinical outcomes in patients with differentiated thyroid carcinoma has rarely been reported and remains controversial.”
In a retrospective study, Kim and colleagues analyzed data from 720 patients with intermediate- or high-risk papillary thyroid carcinoma (PTC) who underwent total thyroidectomy and received their first post-thyroidectomy radioactive iodine treatment between 2000 and 2012 at Asan Medical Center in South Korea. Researchers stratified patients according to timing of the first post-thyroidectomy radioactive iodine treatment: an early group that underwent radioactive iodine therapy less than 90 days after thyroid surgery (n = 360; mean age, 47 years; 14% men), and a delayed group that underwent treatment between 90 and 180 days after thyroid surgery (n = 360; mean age, 48 years; 22% men). They used propensity score matching according to individual risk factors. Primary outcome was initial response to therapy within 2 years of follow-up, categorized as excellent, indeterminate, biochemical incomplete or structural incomplete response, based on serum thyroglobulin, thyroid antibody levels and imaging analysis. Secondary outcomes were disease recurrence and mortality.
After 2 years of follow-up, the number of patients classified into excellent, indeterminate, biochemical incomplete and structural incomplete response categories were 221 (61%), 74 (21%), 39 (11%) and 26 (7%) in the early group, respectively, and 204 (57%), 73 (20%), 59 (16%) and 24 (7%) in the delayed group, respectively, according to researchers. There were no differences between early vs. delayed treatment groups in response to initial therapy based on dynamic risk stratification.
During a median 8.6 years of follow-up, researchers did not observe between-group differences in disease-free survival or overall survival curves. Delayed radioactive iodine therapy was not associated with worse disease-free survival (HR = 1.3; 95% CI, 0.9-1.8) or overall survival (HR = 1.5; 95% CI, 0.6-3.4).
“While additional studies are needed to provide an appropriate time interval between the thyroid surgery and the first [radioactive iodine therapy], concerns about urgent administration of [radioactive iodine] are not justified,” the researchers wrote. “Therefore, it may be safe to perform the first [radioactive iodine] administration at any time until 180 days after total thyroidectomy, even in high-risk patients.”
The researchers noted that because the difference in timing of radioactive iodine administration was modest between groups, there is still a possibility that a longer time difference may have an impact on disease outcomes. – by Regina Schaffer
Disclosures: The authors report no relevant financial disclosures.