Analysis of delayed initial radioactive iodine therapy and clinical outcomes in papillary thyroid cancer: a two-center retrospective study

Background It remains unclear whether the time interval between total thyroidectomy and radioactive iodine (RAI) therapy influences clinical outcomes in papillary thyroid carcinoma (PTC). This study aims to evaluate the impact of the timing to initiate RAI therapy on the response in PTC patients. Methods We retrospectively included 405 patients who underwent total thyroidectomy and subsequent RAI therapy at two tertiary hospitals in southwest China. Patients were categorized into two groups based on the interval between thyroidectomy and initial RAI therapy, that is, an early group (interval <= 90 days, n = 317) and a delayed group (interval >90 days, n = 88). Responses to RAI therapy were classified as excellent, indeterminate, biochemical incomplete, or structural incomplete. Univariate and multivariate analyses were conducted to identify factors associated with a nonexcellent response. Results Excellent responses were observed in 77.3% of the early group and 83.0% of the delayed group (P = 0.252). No significant impact of RAI therapy timing was also observed across all American Thyroid Association risk classification categories. These findings persisted when patients were analyzed separately according to RAI dose (intermediate-dose group: 3.7 GBq [n = 332]; high-activity group: >= 5.5 GBq [n = 73]), further subdivided by the timing of RAI therapy. Multivariate analysis identified lymph node dissection, RAI dose, and stimulated thyroglobulin as independent risk factors for excellent response (P < 0.05). Conclusion The timing of initial RAI therapy following surgery did not significantly affect outcomes in patients with PTC.