Endocrine Abstracts

Background: Distant metastases develop in approximately 5–10% of patients with differentiated thyroid cancer (DTC). Nearly 70% of this subset will become radioiodine refractory (RAI-R) with a poor prognosis. Recently, the multikinase inhibitors (MKIs) showed promising results of treating these patients. It has become crucial to identify RAI-R DTC early. This study was conducted to identify the predictors of RAI-R disease in patients with distant metastasis secondary to differentiated thyroid carcinoma (DTC).

Methods: A retrospective review of 1665 patients with DTC treated at a regional tertiary hospital in Kaohsiung, Taiwan between 1986 and 2010 was performed. Medical records relating to a total of 207 patients with pathologically verified DTC were studied, and all of whom were found to have distant metastasis at diagnosis or during follow-up. Predictor analysis included age, sex, histology, cancer stage, site of metastatic foci, thyroglobulin (Tg) level and accumulated therapeutic dose of radioiodine (RAI). Cases with positive anti-Tg antibody were excluded from analysis.

Results: Approximate 80% of this cohort had papillary carcinoma or its variants whereas others reported follicular carcinoma. The mean age at diagnosis of distant metastasis was 46 years. The female‐to‐male ratio was 2:1. The independent predictors of radioiodine refractory disease were old age (> 55 yr) and high TSH-stimulated Tg level (> 400 mg/l) at the discovery of metastasis.

Conclusion: High level of TSH-stimulated serum Tg levels can be used as a indicator in DTC patients with distant metastasis to predict RAI-R disease. Old age is also a risk factor of RAI-R disease.