Outcomes and Prognostic Factors in Radioiodine Refractory Differentiated Thyroid Carcinomas

Background. Outcomes vary among patients with radioiodine refractory (RR) differentiated thyroid cancer (DTC). The prognostic factors for survival are not well-known, resulting in difficulty in selecting patients for new targeted therapies. We assessed overall survival (OS) and cancer-specific survival (CSS) from RR-DTC to identify prognostic factors associated with survival. Patients and Methods. The data on all cases of metastatic RR-DTC treated in our center from 1990 to 2011 were retrospectively reviewed. Survival was estimated using the Kaplan-Meier method; associated prognostic factors were assessed using Cox’s model. Results. Of 153 cases of metastatic DTC, 59% (n = 91) met a criterion for RR: that is, 60% (n = 55) had at least 1 metastasis without 131I uptake; 21% (n = 19) had progressive disease (PD) despite 131I; 19% (n = 17) had persistent disease despite a cumulative activity of 131I of ≥600 mCi. After the diagnosis of RR, median OS was 8.9 years (95% confidence interval [CI]: 5.4-NR); median CSS was 9.6 years (95% CI: 6.01-NR). In multivariate analyses, PD despite 131I as a criterion for RR disease and the time from initial diagnosis of DTC to diagnosis of RR 1 year or negative Tg-DT. Conclusion. The identification of prognostic factors for decreased survival in RR-DTC may improve the selection of patients for targeted agents.