Abstract
BACKGROUNDS: Patients with differentiated thyroid cancer (DTC) and bone metastases (BM) exhibit heterogeneous radioactive iodine (RAI) and fluorine-18-fluorodeoxyglucose ((18)F-FDG) uptake patterns at diagnosis. This study is aimed to evaluate clinical outcomes influenced these distinct uptake patterns. METHODS: Patients confirmed DTC with BM were involved in this study between 2006 and 2021. All patients received (131)I treatment and performed (18)F-FDG positron emission tomography with computed tomography (PET/CT) at diagnosis. Variables including patient's gender, age, pathology, laboratory examination, uptake pattern of bone lesions, treatment protocols, and metabolic parameters of PET/CT were analyzed for the prognosis. RESULTS: Among 67 enrolled DTC patients with BM, three uptake patterns were identified: RAI+/PET- (18 patients, 26.9%), RAI+/PET+ (40 patients, 59.7%), and RAI-/PET+ (9 patients, 13.4%). Univariate analysis revealed that age stratification, serum thyroglobulin (Tg) levels, and BM uptake pattern significantly impacted progression-free survival (PFS) and overall survival (OS). Critically, RAI+/PET + patients with RAI(+) ratio > 50% showed better PFS (range 12-156 months, median 38.5 months, p = 0.000) and OS (range 20-156 months, median 61.5 months, and p = 0.012) than those with RAI(+) ratio [Formula: see text]50% (PFS: range 6-92months, median 24 months; OS: range 28-112 months, median 51 months). Multivariate analysis identified total total lesion glycolysis of all bone lesions (tTLG) from PET/CT as an independent prognostic factor for both PFS and OS (p = 0.021 and p = 0.035, respectively). CONCLUSIONS: The RAI(+) ratio determines clinical outcomes, and the prognosis of RAI+/PET + patients resembles that of RAI+/PET- patients, suggesting similar biological behavior in DTC patients with BM. Pretreatment tTLG is a significant independent prognostic marker for PFS and OS.