Prognostic significance of systemic inflammatory and peripheral immune profiles in differentiated thyroid carcinoma: a retrospective cohort study

Although differentiated thyroid carcinoma (DTC) generally has a favorable prognosis, a subset of patients develop aggressive disease associated with poor outcomes. Current risk stratification relies mainly on clinicopathological features, whereas circulating inflammatory and immune biomarkers may provide complementary prognostic information. This study aimed to evaluate the prognostic significance of systemic inflammatory status, thyroid-related biomarkers, and peripheral immune profiles in patients with DTC. We retrospectively analyzed 430 patients with pathologically confirmed DTC who underwent surgical resection. Preoperative inflammatory markers, thyroid-related biomarkers, and peripheral immune cell profiles were evaluated, and their associations with overall survival (OS) were assessed using Kaplan–Meier analysis and Cox proportional hazards regression models. Compared with healthy controls and patients with benign thyroid nodules, patients with DTC exhibited significantly elevated levels of the systemic immune-inflammation index (SII), thyroglobulin (Tg), and thyroglobulin antibody (TgAb) (all P < 0.001). Higher levels of SII, Tg, and TgAb were associated with lymph node metastasis and distant metastasis. Multivariable Cox regression analysis identified older age, follicular thyroid carcinoma, lymph node metastasis, distant metastasis, elevated SII, increased Tg and TgAb levels, and higher CD8⁺ T-cell proportion as independent predictors of inferior OS. Kaplan–Meier analyses further demonstrated that higher proportions of CD3+, CD4+, and CD19 + cells and lower proportions of CD56 + cells were associated with improved OS, whereas CD127 + cell proportion showed no significant association with OS. Systemic inflammatory status, thyroid-related biomarkers, and peripheral immune cell profiles provide complementary prognostic information in patients with DTC. Integration of SII, Tg/TgAb levels, and immune profiling may complement existing risk stratification approaches and facilitate individualized postoperative risk assessment and surveillance.