Prediction of Treatment Response by Thyroid Bed Uptake on Post-Ablative Whole-Body Scan in Intermediate-Risk Patients...

Background/Objectives: This study aimed to evaluate the prognostic significance of thyroid bed uptake on post-ablative whole-body scan (PAWBS) in predicting treatment response in intermediate-risk papillary thyroid carcinoma (PTC) patients undergoing high-dose radioactive iodine (RAI) therapy following total thyroidectomy. Methods: This retrospective study included 148 intermediate-risk PTC patients who underwent high-dose RAI therapy after total thyroidectomy. PAWBS was performed 7 days post-therapy, and thyroid bed uptake was visually graded. Treatment response was assessed using stimulated thyroglobulin (sTg) levels, imaging studies, and clinical follow-up. Responses were classified into excellent, indeterminate, biochemical incomplete, or structural incomplete categories. Logistic regression analyses were conducted to identify predictors of treatment response. Results: Among the 148 patients, 126 (85.1%) achieved an excellent response (ER), while 22 (14.9%) showed a non-excellent response (NER), which included indeterminate, biochemical incomplete, and structural incomplete responses. Patients with NER exhibited significantly higher thyroid bed uptake on PAWBS compared to ER patients (p = 0.001). Multivariate analysis revealed that higher thyroid bed uptake was an independent negative prognostic factor for achieving an excellent response (p < 0.001), along with sTg (p < 0.001). Conclusions: The intensity of thyroid bed uptake on PAWBS independently predicts treatment response in intermediate-risk PTC patients receiving high-dose RAI therapy, with higher uptake indicating a worse prognosis.