Endocrine Abstracts

The ability of thyroid cell to accumulate iodine is due to presence of sodium iodide symporter (NIS). Differentiated thyroid cancer (DTC) maintain ability to express NIS and thus it makes possible to perform RAI treatment. In case of DTC cells loss the ability of NIS protein production and cell membrane embedding that leads to RAI treatment fail.

The aim of our study was to find a relationship between the level of preoperatively defined NIS and recurrences-free survival after RAI in DTC patients.

Materials and methods: Our study included 205 patients with highly differentiated thyroid cancer. In all patients the level of NIS expression was detected by flow fluorocytometry method in a fine-needle biopsy material. The criteria for inclusion in the study were RAI therapy in the postoperative period, the ability to follow up the patient in the postoperative period up to 60 months. All patients were operated.

Results: RAI therapy was performed in 130 patientsin the postoperative period. Recurrence was detected in 50 patientsin the follow-up period of 60 months. Total thyroidectomy (TT) with central lymph node dissection (CLD) was performed in 72.5% (58/80) of cases in the group without recurrence, compared with the group of patients with detected recurrence, where this operation was performed only in 24% (12/50) of cases. Lateral neck compartment cervical lymph node dissection was performed in 40% of patients in the group with developed recurrence of the disease and in 17.5% of patients without recurrence of the disease. The liner discriminant analysis (LDA) revealed the level of NIS expression less than 1% significantly correlate with the risk of recurrence (P = 0.000037). In the group of patients with recurrence, the level of NIS expression less than 1% was detected in 31 patients (62%), while in the group without recurrence only in 17 (21.2%).Thus, the recurrence-free survival after RAI is significantly lower in patients with NIS expression less than 1% in primary tumor compared to patients with NIS expression level more than 1%. TT with CLD was performed in all patients with low NIS expression in the group without disease recurrence and decrease in the number of recurrences is possibly associated with the volume of surgical treatment.

Conclusions: The level of NIS expression can be used as a prognostic marker of disease recurrence, particular after RAI. The level of NIS expression less than 1% in the primary tumor is suspicious of RAI-refractory DTC.