Focus on high-risk DTC patients: high postoperative serum thyroglobulin level is a strong predictor of disease persistence and is associated to progression-free survival and overall survival.

Introduction: No parameters predicting recurrence are available for high-risk differentiated thyroid cancer (DTC) patients, and 2-year-follow-up is required to modify the initial prognostic classification. High thyroglobulin (Tg) levels before ¹³¹I-remnant-ablation, during L-thyroxine-withdrawal (ablation-Tg) have undetermined predictive/prognostic significance in low-risk DTC patients. Our study aimed to assess the positive predictive value (PPV) of ablation-Tg in high-risk DTC patients and to evaluate whether high ablation-Tg levels were associated with progression-free-survival (PFS) and overall survival (OS).

Patients And Methods: We selected 243 high-risk DTC patients. All patients underwent total thyroidectomy and ¹³¹I-remnant-ablation (initial therapy). Clinical data obtained during a median 5-year follow-up were used to assess the response and outcome. The association between disease persistence/recurrence after initial therapy, ablation-Tg, and other risk-factors (T, N, G, histology, and MACIS score) was evaluated through univariate and multivariate analyses, as was the association between PFS, OS ablation-Tg, and other risk factors.

Results: Ablation-Tg of 50 μg/L or greater displayed the highest PPV(97%) for disease persistence. In the univariate analysis, high levels of ablation-Tg were confirmed in patients with persistent disease after initial therapy: the higher the odds ratios, the higher the ablation-Tg levels. On multivariate analysis, ablation-Tg was the best predictive factor, especially on comparing patients with ablation-Tg levels of 50 μg/L or greater and those with ablation-Tg less than 2 μg/L (adjusted OR, 818). In a multivariate Cox model, ablation-Tg was the factor most closely associated with PFS (HR, 65.9). The prognostic value of ablation-Tg was confirmed by the overall-survival curves and adjusted risk estimates (adjusted HR=26.7).

Conclusions: Ablation-Tg levels of 50 μg/L or greater are a valuable initial predictor of disease persistence/recurrence in high-risk DTC patients. A significant association emerged between high ablation-Tg levels of 50 μg/L or greater and both progression-free survival (PFS) and overall survival (OS).