The effect of sodium iodide symporter protein on ablation success in patients with differentiated thyroid cancer

The aim of this study was to investigate immunohistochemical staining of sodium iodide symporter and it's effect on response to I-131 therapy in differantiated thyroid carcinoma patients. We evaluated NIS expression, intracellular distrubition of NIS, iodine-131 uptake in residuel tissues on postablation I-131 whole body scan and the ablation status after 100 mCi I-131 therapy. We also investigated NIS expression and localization in tumoral paraffin-embedded tissues. In this retrospective study, a total of 35 patients (mean age 44.17 ± 12.9 years, 27 female, 8 male) were studied. 21 of these patients responded to radioiodine therapy and 14 did not. The difference was not statistically significant between NIS expression and iodine-131 uptake in residuel tissues on postablation I-131 whole body scan. When we compared the patients who responded to radioiodine therapy and poor responder group, NIS expression and iodine-131 uptake in residuel tissues didn't demonstrate statistically significant difference [ (p=0.308) (p=0.985) respectively ]. 47.6% of the patients in good responder group and 78.6% of poor responder group had intracellular NIS immunostaining. 52.4% of the patients in good responder group and 14.3% of poor responder group had NIS immunostaining at the basolateral membrane. The difference was not statistically significant[ (p=0.139) (p=0.054) respectively ]. There were 41 tumor foci among 35 patients' specimens. 27 tumor foci were examined in good responder group, 14 tumor foci were examined in poor responder group. 5 patients had more than one tumor focus. NIS positive staining were obtained from 20 foci in good responder group and 9 foci in poor responder group. When we evaluate the total NIS staining area on tumor foci, an area of 60.9% had positive staining in good responder group and 43.8% in poor responder group. In both groups intracellular staining was predominant. In conclusion, to evaluate iodine-131 uptake in residuel tissues, ablation status and prognosis in differentiated thyroid carcinoma patients, comparison should be done between the serum TSH levels at the time of surgery, NIS expression in tumoral and nontumoral tissues and intracellular distrubition of NIS in a large number of patients with a long term follow-up.