Longitudinal dynamics of symptom networks in patients with differentiated thyroid cancer undergoing radioactive iodine therapy: a prospective cohort study

BackgroundPatients with differentiated thyroid cancer (DTC) undergoing radioactive iodine (RAI) therapy experience concurrent physical and psychological symptoms, yet the dynamic interplay among these symptoms remains incompletely characterized.ObjectiveTo characterize longitudinal changes in symptom network structure during RAI therapy and identify core and bridge symptoms across treatment phases.MethodsThis prospective cohort study enrolled 520 DTC patients receiving RAI therapy. Symptoms were assessed at three timepoints: pre-treatment (T0), 48 hours post-treatment during radiation isolation (T1), and one week after discharge (T2). Gaussian graphical models were estimated using graphical LASSO with extended Bayesian information criterion. Strength centrality, bridge centrality, and predictability were calculated. Network comparison tests examined structural differences across timepoints.ResultsNetwork structure differed significantly across timepoints (T0-T1: M = 0.306, P = 0.001; T0-T2: M = 0.347, P = 0.001), while global strength remained stable (P = 0.124-0.582). Psychological distress consistently exhibited the highest strength centrality (T0: 1.405; T1: 1.473; T2: 1.640) and bridge strength (T0: 0.755; T1: 0.767; T2: 0.976). Throat/mouth symptoms emerged as a critical bridge connecting physical and psychological symptom clusters after RAI (bridge strength: T0 = 0.107; T1 = 1.017; T2 = 1.016). Predictability of treatment-related physical symptoms increased substantially from near-zero at T0 to high levels at T1-T2 (e.g., throat/mouth symptoms: 0.064 to 0.782), indicating rapid network integration following treatment.ConclusionsRAI therapy is associated with substantial network reorganization rather than simple symptom accumulation. Psychological distress maintains central importance throughout, with increasing prominence post-treatment. Throat/mouth symptoms serve as critical bridges between physical and psychological domains. These findings suggest that the treatment-to-surveillance transition may represent an important window for psychological intervention, and that bridge symptoms such as throat/mouth discomfort merit further investigation as candidate targets for improving symptom management in DTC patients.