The clinical impact of 131-iodine whole-body scintigraphy following 131-iodine therapy of thyroid cancer

The incidence of thyroid cancer has increased globally and in Denmark. Following total thyroidectomy, patients at intermediate or high risk undergo radioactive iodine (RAI) therapy with 131I to ablate residual thyroid tissue and treat potential metastases. European and American guidelines recommend post-treatment whole-body scintigraphy (WBS) 2–10 days after RAI to supply information on disease staging. This study evaluated whether post-treatment 131I WBS findings influenced subsequent clinical management for the patients. In this retrospective cohort study, 363 patients received RAI at Herlev University Hospital between January, 2021, and February, 2024. Post-treatment 131I WBS was available in 330 patients (91% - the study group). In a subgroup analysis, patients with negative scans, known metastases, or prior RAI therapy were excluded. Medical records were reviewed to determine whether WBS findings led to changes in management, defined as additional RAI therapy, supplementary imaging, or modification of follow-up. Among the 330 patients, 249 (76%) high-risk patients received 3.7 GBq, 80 (24%) intermediate-risk patients received 1.1 GBq, and one pediatric patient received 2.0 GBq. No intermediate-risk patients showed iodine-avid foci beyond residual neck uptake. Among the 298 patients who received adjuvant RAI without known metastatic disease, 15 had suspected metastases on WBS, of whom only six (2%) experienced a management change. ost-treatment 131I WBS rarely influenced decision-making, affecting only 2% of adjuvant RAI patients. Given the overall good prognosis and limited clinical impact, the routine use of post-treatment 131I WBS, particularly in intermediate-risk patients, may warrant reconsideration in future guidelines.