Stimulated thyroglobulin and Thyroglobulin Reduction Index Predict Excellent Response in Differentiated Thyroid Cancers.

CONTEXT: Despite its good prognosis, differentiated thyroid cancer (DTC) is characterized by high rates of disease persistence and recurrence. Estimation of long-term remission (excellent response) thanks to specific parameters could help to individualize the active surveillance schedule. OBJECTIVE: Evaluation of the ability of stimulated thyroglobulin (Tg) and Tg reduction index (TRI) to predict long-term remission in patients with DTC managed by thyroidectomy and radioactive iodine (RAI) remnant ablation. PATIENTS AND INTERVENTIONS: Observational retrospective study of 1093 patients treated for DTC between 1995 and 2010. Preablation stimulated thyroglobulin (presTg) was measured under thyroid hormone withdrawal just before RAI. Recombinant human TSH-stimulated thyroglobulin (sTg) was measured at first evaluation of the initial management 6 to 12 months after RAI. TRI was calculated based on pre-Tg and sTg. RESULTS: After univariate and multivariate analyses, lymph node invasion (N1, OR = 2.08; 95% CI, 1.19 to 3.64), presTg (OR = 4.04; 95% CI, 2.56 to 6.38), sTg (OR = 2.62; 95% CI, 2.05 to 3.34), and TRI (OR = 0.43; 95% CI, 0.21 to 0.88) were identified as independent prognostic factors influencing the rate of disease persistence or recurrence after the initial management. Receiver operating characteristic analysis identified presTg cutoff ( 60% for the entire cohort and 62.5% for locally advanced disease (T3/T4, N1) was sensitive predictor for excellent response. CONCLUSION: This study identifies presTg, sTg, and TRI as highly sensitive predictors of excellent response in patients with DTC and subsequently disease-free status. The cutoff of such parameters is also adapted for patients with higher tumor stages (T3/T4, N1).