Prognostic value of serum thyroglobulin level at the time of lithium combined radioactive iodine therapy in patients with differentiated thyroid cancer with distant metastasis

Objectives To investigate whether serum thyroglobulin level at the time of lithium combined radioactive iodine (RAI) therapy could predict outcome of differentiated thyroid cancer (DTC) with distant metastasis.

Methods A total of 28 patients with DTC with distant metastasis were enrolled. All patients underwent total thyroidectomy and lithium combined RAI therapy. Patients with positive anti-Tg antibodies were previously excluded. Serum levels of TSH-stimulated thyroglobulin at the time of first lithium combined RAI therapy (offTg), pretreatment thyroglobulin on thyroxine (onTg#1), and posttreatment thyroglobulin on thyroxine (onTg#2) were checked. The progression free survival (PFS) and overall survival (OS) of patients were analyzed by diverse clinical factors such as age, sex, histologic type, additional operation, external radiotherapy, occasions and cumulative dose of RAI therapy, offTg, Tg#1, and onTg#2. The relationships between covariates and survival were analyzed using Kaplan-Meier method.

Results The median PFS and OS were 14 months (3-66 months) and 58 months (9-68 months), respectively. On univariate analysis, old age (p = 0.0026), higher cumulative dose of previous RAI therapy (p = 0.037), follicular carcinoma (p = 0.014), higher offTg (p = 0.0061), higher onTg#1 (p = 0.018), and higher onTg#2 (p = 0.0051) were significantly associated with poorer PFS. And old age (p = 0.030), more occasions of previous RAI therapy (p = 0.036), higher offTg (p = 0.0051), higher onTg#1 (p = 0.0002), and higher onTg#2 (p = 0.0051) were significantly associated with poorer OS.

Conclusions Serum thyroglobulin level at the time of lithium combined RAI therapy has a prognostic value in patients with DTC with distant metastasis.

Research Support None.