Relationship between expression of the sodium/iodide symporter and I-131 uptake in recurrent lesions of differentiated thyroid carcinoma

The sodium/iodide symporter (NIS) is known to be responsible for the active accumulation of iodide within the thyroid gland. We evaluated the relation ship between the expression of NIS in primary or lymph node lesions and iod ine-131 uptake in recurrent lesions of differentiated thyroid cancer. In 67 patients with differentiated thyroid cancer (5 follicular and 62 papillary carcinomas), the expression of NIS was analysed by immunohistochemical sta ining using polyclonal antibodies against human NIS. We used paraffin block tissues of primary tumours or metastatic lesions, and also assessed I-131 uptake in recurrent lesions of thyroid cancer on postoperative I-131 whole- body scan. Immunohistochemical staining was positive in 22 patients (32.8%) , including 2 of 5 follicular and 20 of 62 papillary carcinomas. Recurrence was confirmed in 40 patients pathologically or clinically by serum thyrogl obulin, I-131 scan, fluorine-18 fluorodeoxyglucose positron emission tomogr aphy and/or computed tomography. Among these 40 patients, 28 showed positiv e uptake on I-131 scan. Fourteen tumour specimens out of 28 (50%) were posi tive by NIS immunohistochemical staining. The remaining 12 patients with re current cancer showed negative I-131 scans, and all specimens were negative by NIS immunohistochemical staining. Thus, NIS immunohistochemical stainin g predicted I-131 uptake in recurrent cancer with a 100% positive predictiv e value and a 46.2% negative predictive value, There was no difference in t he positivity of NIS according to the site of recurrence on I-131 scan. Out come of I-131 therapy could be assessed in 22 of the 28 patients who showed I-131 uptake in recurrent lesions. Patients with positive NIS immunostaini ng responded to I-131 therapy better than did patients with negative immuno staining (P<0.05). In conclusion, NIS immunohistochemical staining showed a high positive predictive value in predicting iodine uptake. Positive immun ohistochemical staining of human NIS in primary or lymph node lesions may p redict I-131 accumulation and effectiveness of I-131 therapy in recurrent l esions.