The aim of our study was to evaluate and compare in thyroid cancer patients the predictive value for disease progression of thyroglobulin (Tg) levels measured under thyroid-stimulating hormone (TSH) stimulation, in the postoperative period just before (131)I ablative therapy and at the time of control 6-12 mo later.
Methods: Two-hundred twelve consecutive patients treated for a well-differentiated thyroid carcinoma (184 papillary, 28 follicular) with no initial distant metastases were retrospectively studied. All patients had a total or near-total thyroidectomy followed by ablation with 3.7 GBq (131)I. Tg levels were determined just before ablative therapy (Tg1) and 6-12 mo later (Tg2). Thresholds of 30 and 10 ng/mL were used for Tg1 and Tg2, respectively. Univariate and multivariate analyses were performed to assess the predictive value for disease progression of the 2 Tg determinations.
Results: Thirty patients had a Tg1 level > 30 ng/mL. Six to 12 mo later, 30 patients had a Tg2 level > 10 ng/mL, 19 of whom had initially a Tg1 level > 30 ng/mL. Disease progression was reported in 20 patients (9%). Progression-free survival rates were significantly lower in patients with a low Tg1 or Tg2 level but the difference was more important with Tg2. With univariate analysis, 5 variables were significantly associated with disease progression: Tg2, Tg1, node invasion, extrathyroidal extension, and tumor size. With multivariate analysis, only Tg2 (odds ratio [OR] = 16.4; 95% confidence interval [95% CI] = 5.7-47.4; P < 0.001) and node invasion (OR = 2.7; 95% CI = 1.0-7.2; P = 0.04) had an independent prognostic value. When only initial parameters were considered, Tg1 and node invasion were the 2 independent prognostic factors. The OR decreased for Tg1 (OR = 10.1; 95% CI = 4.0-25.7; P < 0.001) but increased for node invasion (OR = 4.4; 95% CI = 1.7-11.2; P = 0.002).
Conclusion: Among all clinical and tumoral variables, lymph node invasion and serum Tg level are 2 important parameters to define the risk of disease progression. Although Tg2 appears more significant than Tg1, both Tg levels measured under TSH stimulation, in the postoperative period and a few months after ablative therapy, have a predictive value. In clinical practice, patients at risk can be selected as soon as the initial lymph node status and Tg1 level are known.