Impact of delayed radioiodine therapy in intermediate-/high-risk papillary thyroid carcinoma

It remains unclear whether the time interval between total thyroidectomy and radioactive iodine therapy (RAIT) affects clinical outcomes in papillary thyroid carcinoma (PTC). Therefore, we evaluated the impact of timing of the first post-thyroidectomy RAIT in intermediate-to-high-risk PTC.

This retrospective propensity score-matched cohort study included 720 PTC patients who received RAIT for <90 or 90-180 days (early and delayed groups, n = 360 each) after thyroidectomy. Responses to therapy, disease-free survival (DFS) and overall survival (OS) were compared between the two groups.

After matching, the baseline characteristics of the 360 patients in each group were similarly adjusted. Within the first 2 years after initial therapy, 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, and 204 (57%), 73 (20%), 59 (16%) and 24 (7%) in the delayed group, respectively. There was no significant difference in response to therapy between the two groups (P = 0.183). During the median follow-up of 8.6 years, there was no significant difference in DFS (P = 0.060) and OS (P = 0.400) curves between the two groups. Delayed RAIT was not significantly associated with worse DFS (HR = 1.3, 95% CI 0.9-1.8, P = 0.061) or OS (HR = 1.5, 95% CI 0.6-3.4, P = 0.388).

Delaying the first RAIT until 180 days after total thyroidectomy had no impact on restaging, recurrence and mortality in intermediate-to-high-risk PTC.