MON-548 The Relationship of Comorbidities to Mortality and Cause of Death in Patients with Differentiated Thyroid Carcinoma

Background: Understanding how comorbidities contribute to death in cancer patients is becoming an important topic. The present study assessed the role of comorbidities in overall mortality and causes of death in patients with differentiated thyroid carcinoma (DTC). Methods: This retrospective cohort study included 2070 patients who underwent thyroidectomy for DTC at a single institution between 2002 and 2005. Probabilities of overall, DTC-specific, and other-cause death were examined according to estimated comorbidity levels with consideration for competing events. Results: The estimated 15-year cumulative incidences of overall, DTC-specific, and other-cause death were 7.3%, 1.6%, and 5.7%, respectively. With the low comorbidity level as a reference, moderate and severe comorbidity levels were associated with higher probabilities of other-cause death (subhazard ratio = 3.82 and 18.94, respectively; p <0.001) and consequently shorter overall survival (hazard ratio = 2.94 and 12.24, respectively; p <0.001), with adjustment for age, sex, and tumor-node-metastasis stage. In contrast, the probability of DTC-specific death was reduced in patients with severe comorbidity level (subhazard ratio = 1.24e-6, p <0.001). DTC-specific death was only observed in patients with low comorbidity level or with stage III/IV DTC and moderate comorbidity level. Conclusion: Death from DTC itself accounted for only a fraction of the overall deaths among patients who underwent surgery for DTC. Comorbidities increased overall mortality by increasing the probability of other-cause death. Patients with severe comorbidities had a low probability of dying from DTC because they died earlier from comorbidities.