Poorly Differentiated Thyroid Carcinoma Patients with Detectable Thyroglobulin Levels after Initial Treatment Show an Increase in Mortality and Disease Recurrence

Abstract

Purpose: The role of thyroglobulin (Tg) in predicting death and recurrence risk in patients with poorly differentiated thyroid carcinoma (PDTC) is not well established. We aimed to analyze Tg levels following total thyroidectomy and adjuvant radioiodine treatment (RAI) in PDTC patients and correlate Tg levels with survival and recurrence. Methods: A retrospective analysis was conducted on 101 patients with PDTC who were treated between 1986 and 2010. Among them, 38 had no distant metastases at presentation, were managed by total thyroidectomy and adjuvant RAI, and had negative anti-Tg antibodies. An unstimulated Tg level < 1 ng/mL was used as a cut-off point for undetectable Tg levels. Association of patient and tumor characteristics with Tg levels was examined by χ² test. Overall survival, disease-specific survival (DSS), and recurrence-free survival (RFS), stratified by Tg levels, were calculated by the Kaplan-Meier method and compared by the log-rank test. Results: Compared to patients with undetectable Tg, cases with detectable Tg had a lower probability of achieving free surgical margins (21.7 vs. 46.7%; p = 0.04), higher node status (73.3 vs. 21.8%; p = 0.005), decreased 5-year DSS (65 vs. 100%; p = 0.009), and worse 5-year RFS (32 vs. 84%, p = 0.010), with a significant number of patients having a recurrence in the first year (50 vs. 12.5%; p = 0.021). Patients with detectable Tg levels also showed worse locoregional (55.6 vs. 90.9%; p = 0.014) and distant control (5-year distant control of 46.9 vs. 91%; p = 0.017). Conclusions: Our results suggest that detectable Tg levels after surgery and RAI in a subset of PDTC patients appear to predict a higher rate of death and recurrence.