Outcomes and Prognostic Factors in Radioiodine Refractory Differentiated Thyroid Carcinomas

Abstract

© AlphaMed Press 2016. 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 RRDTC 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 131 I uptake; 21% (n519) had progressive disease (PD) despite 131 I; 19% (n = 17) had persistent disease despite a cumulative activity of 131 I 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 131 I asa criterion for RR disease and the time from initial diagnosis of DTC to diagnosis of RR < 3 years were the only independent prognostic factors for poor OS and CSS. Thyroglobulin doubling time (Tg-DT) was assessed in 31 of 91 cases. Among the 11 patients with Tg-DT for < 1 year or undetectable Tg, 6 deaths occurred, whereas only 3 died of 20 patients with Tg-DT > 1 year or negative Tg-DT. Conclusion. The identification of prognostic factors fordecreased survival in RR-DTC may improve the selection of patients for targeted agents.