Impact of thyroglobulin changes on clinical outcomes of differentiated thyroid cancer with biochemical incomplete...

Partial patients with biochemical incomplete response (BIR) after initial therapy for differentiated thyroid cancer (DTC) may progress to structural recurrence during follow-up. For better-individualized care, this study analyzed predictors of structural recurrence in patients with BIR after initial radioactive iodine therapy (RAIT).

A retrospective study was conducted on 4,263 patients with DTC who underwent thyroidectomy and initial RAIT between June 2009 and August 2023. Patients with either suppressed thyroglobulin (Sup-Tg) > 1 ng/mL or stimulated Tg (Sti-Tg) > 10 ng/mL and negative anti-Tg antibodies (TgAb < 40 IU/mL) without structural disease were enrolled. Pathological examination or imaging confirmed structural recurrence. Sup-Tg change level [ΔSup-Tg% = (Sup-Tg_3rd - Sup-Tg_2nd)/Sup-Tg_2nd × 100%] and other clinicopathological parameters were used to predict structural recurrence in patients with BIR.

We enrolled 161 patients with a median follow-up of 6.3 years. Fourteen patients (8.7%) progressed to structural disease, 80 (49.7%) remained in BIR status, and 67 (41.6%) recovered with long-term remission. ΔSup-Tg%≥17.08% displayed high specificity (84.4%) for structural recurrence prediction (AUC = 0.705, p = 0.011). Extrathyroid extension, stage III and ΔSup-Tg% were independent predictors of structural recurrence (OR = 4.568, p = 0.038; OR = 9.594, p = 0.015; and OR = 18.781, p < 0.001, respectively). Kaplan-Meier analysis showed that these factors were associated with structural recurrence-free survival. Cox regression analysis found that patients with stage III and ΔSup-Tg%≥17.08% have a higher risk of recurrence (HR = 4.818, p = 0.015 and HR = 10.173, p < 0.001, respectively).

Longitudinal monitoring of Tg is essential and Tg change level could be used as a predictor of structural recurrence in patients with BIR.