BACKGROUND: The aim of this study was to assess the efficacy of radioactive iodine-131 (¹³¹I) therapy for lymph node metastasis of differentiated thyroid cancer (DTC) and to identify influential factors using univariate and multivariate analyses to determine if identified factors influence the efficacy of treatment.

MATERIAL AND METHODS: This study included a retrospective review of 218 patients with histologically proven DTC in the post-operation stage. After thyroid tissue remnants were eliminated with ¹³¹I therapy, patients’ lymph node status was confirmed by ultrasound and by ¹³¹I whole body scan regarding lymph node metastasis, and then patients were treated with ¹³¹I as appropriate. The treatment efficacy was assessed and possible influencing factors were identified using univariate and multivariate analyses.

RESULTS: The total effective rate of ¹³¹I therapy was 88.07% (including a cure rate of 20.64% and an improvement rate of 67.43%). The non-effective rate was 11.93%. Of the total 406 lymph nodes of 218 patients, 319 lymph nodes (78.57%) were judged to be effectively cured, including 133 (32.75%) lymph nodes that were totally eliminated and 186 (45.82%) lymph nodes that shrank. Eighty-seven (21.43%) of the 406 lymph nodes had no obvious change. No lymph nodes were found to be in a continuously enlarging state. Distant metastasis, size of lymph node, human serum thyroglobulin (HTG) level, and condition of thyroid remnants ablation were identified as the independent factors influencing the efficacy of treatment using univariate and multivariate analyses.

CONCLUSIONS: The use of ¹³¹I is a promising treatment for lymph node metastasis of DCT. Distant metastasis, size of lymph nodes, HTG level, and condition of thyroid remnant ablation were independent factors influencing the treatment efficacy.

Keywords: Iodine Isotopes, Lymph Nodes