Clinical management and outcomes in patients with hyperfunctioning distant metastases from differentiated thyroid cancer after total thyroidectomy and radioactive iodine therapy.

Abstract

Hyperfunctioning distant metastasis (HFDM) from differentiated thyroid cancer (DTC) is a rare entity. This study aimed to assess the outcomes of DTC patients presenting with HFDM after total thyroidectomy and radioactive iodine therapy. A total of 5367 DTC patients treated with (131)I after total thyroidectomy were analyzed retrospectively from January 1991 to June 2013. Therapeutic efficacy was evaluated based on changes in serum thyroglobulin (Tg) and anatomical imaging changes in metastatic lesions. The relationships between survival time and several variables were assessed by univariate and multivariate analyses using the Kaplan-Meier method and Cox's proportional hazards model respectively. Thirty-eight patients with HFDM from DTC were diagnosed, including four with hyperthyroidism, four with subclinical hyperthyroidism, and three with subclinical hypothyroidism. The remaining 27 were euthyroid. Of 25 patients with lung metastases, 84% (21/25) showed disappearance or shrinkage of lung nodules; of 24 patients with bone metastases, 66.67% (16/24) exhibited no obvious imaging changes in metastatic bone lesions after (131)I therapy. Serum Tg decreased significantly in 81.58% (31/38) and increased in 18.42% (7/38) after (131)I therapy. The 10-year survival rate of DTC patients with HFDM was 65.79% (25/38). Multivariate analyses identified age at occurrence of distant metastases (<45 years), only lung metastases, and papillary thyroid cancer (PTC; p=0.032, NA, and 0.043) as independent predictors of survival. The response of hyperfunctioning lung metastases to (131)I treatment was better than that of non-hyperfunctioning lung metastases in DTC, while hyperfunctioning bone metastases responded similarly compared to non-hyperfunctioning bone metastases. Patients younger than 45 years at occurrence of distant metastases, those with only lung metastases, and patients with PTC had better prognoses.