Diagnostic performance of 18FTetrafluoroborate PET versus 131I scintigraphy in differentiated thyroid cancer: a prospective study

Abstract Purpose Differentiated thyroid cancer (DTC) is primarily evaluated using radioiodine (RAI) scanning; however, this approach is limited by the suboptimal imaging properties of 131 I, the cost and limited availability of 123 I, and restricted access to 124 I. 18 FTetrafluoroborate (TFB), a PET radiotracer targeting the sodium/iodide symporter, has emerged as a promising alternative. This prospective study assessed the diagnostic performance and biodistribution of TFB PET compared with 131 I scintigraphy in patients with DTC. Methods This prospective study enrolled 58 patients with histopathologically confirmed DTC after total or near-total thyroidectomy. Forty-eight patients underwent both TFB PET/CT and 131 I SPECT scintigraphy, while 10 underwent only TFB PET for biodistribution analysis. Patients were stratified into preradioiodine (TFB before 131 I; n = 28) and postradioiodine (TFB after 131 I; n = 20) subgroups based on recent radioiodine administration (either diagnostic or therapeutic) to evaluate the potential stunning effect of 131 I on TFB uptake. Patient- and lesion-based analyses were performed, and agreement was assessed using Cohen’s kappa. Results In patient-based analysis, concordance between modalities showed both TFB and 131 I positivity in 20 patients, TFB-only positivity in 1 patient, 131 I-only positivity in 5 patients, and negativity in both modalities in 22 patients, yielding substantial overall agreement (κ = 0.75). Agreement was almost perfect in the preradioiodine group (κ = 0.84) but declined to a moderate level in the postradioiodine group (κ = 0.49). In lesion-based analysis ( n = 56), overall detection rates were comparable (TFB, 85.7% vs. 131 I, 73.2%) but significantly higher for TFB in the preradioiodine group (95.7% vs. 68.1%, p < 0.05). Lesion detection decreased markedly in the postradioiodine group (33.3%), consistent with a stunning effect. Biodistribution analysis showed highest physiological uptake in the stomach, salivary glands, esophagus, nasopharynx and unexpected uterine uptake in Nabothian cysts in 45% of female patients. Conclusion TFB PET demonstrates diagnostic accuracy and lesion detection rates comparable to 131 I scintigraphy in DTC. Its diagnostic performance is superior in patients without recent radioiodine administration prior to TFB imaging, whereas lesion detectability decreases after radioiodine administration, likely due to a stunning effect. Therefore, TFB PET represents a promising alternative for disease burden assessment in DTC and warrants further multicenter validation.