Prognosis and prognostic factors of differentiated thyroid carcinoma after the appearance of metastasis refractory to radioactive iodine therapy.

Differentiated thyroid carcinomas (DTCs) are generally indolent, but few therapeutic strategies are available after a metastatic recurrence that is refractory to radioactive iodine (RAI) therapy. Molecular-target therapy has shown promising results for DTCs with RAI-refractory recurrence. However, not all RAI-refractory recurrences are progressive, and even those that are progressive may not be immediately life-threatening. Here we investigated the prognosis and prognostic factors of 74 DTC patients (52 females, 22 males) in whom RAI-refractory metastases appeared. The five-year and 10-year cause-specific survival (CSS) rates of the 74 patients (8-82 yrs of age; median age at the detection of metastases, 61 yrs) were 95% and 70%, respectively, and the older patients (≥ 60 yrs, n=38) and male patients were significantly more likely to die of carcinoma. Also in multivariate analysis, older age (≥ 60 years) and male gender were independent predictors of carcinoma-related death. Taken together, our data indicate that RAI-refractory metastases of older patients and male patients are more progressive than those of other patients. Further studies are necessary to clarify the appropriate indications for molecular-target therapy for RAI-refractory and progressive metastases.