Predictive value for disease progression of serum thyroglobulin levels measured in the postoperative period and after (131)I ablation therapy in patients with differentiated thyroid cancer.

UNLABELLED

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.