Competing Causes of Death in Older Adults with Thyroid Cancer

Understanding the impact of comorbidities and competing risks of death when caring for older adults with thyroid cancer is key for personalized management. The objective of this study was to determine whether older adults with thyroid cancer are more likely to die from thyroid cancer or other etiologies, and determine patient factors associated with each. The Surveillance, Epidemiology, and End Results (SEER)-Medicare database was used to identify patients aged ≥66 years diagnosed with thyroid cancer (papillary, follicular, Hürthle cell, medullary, anaplastic, and other) between 2000 and 2015 (median follow-up, 50 months). We analyzed time to event (i.e., death from other causes or death from thyroid cancer) using cumulative incidence functions. Competing risk hazards regression was used to determine the association between patient (e.g., age at diagnosis and specific comorbidities) and tumor characteristics (e.g., SEER stage) with two competing mortality outcomes: death from other causes and death from thyroid cancer. Of 21,509 patients with a median age of 72 years (range 66-106), 4168 (19.4%) died of other causes and 2644 (12.3%) died of thyroid cancer during the study period. For differentiated thyroid cancer patients, likelihood of dying from other causes exceeds likelihood of dying from thyroid cancer, whereas the opposite is true for anaplastic thyroid cancer. For medullary thyroid cancer, after 6.25 years patients are more likely to die from other etiologies than thyroid cancer. Using competing risks hazards regression, male sex (hazards ratio [HR] 1.47; 95% confidence interval [CI 1.37-1.57]), black race (HR 1.30; CI [1.16-1.46]), and comorbidities (e.g., heart disease, HR 1.34; CI [1.25-1.44]; chronic lower respiratory disease, HR 1.25; CI [1.17-1.34]) were associated with death from other causes. Tumor characteristics such as histology, tumor size, and stage correlated with death from thyroid cancer (e.g., distant SEER stage compared with localized, HR 12.65; CI [10.91-14.66]). The clinical context, including patients' specific comorbidities, should be considered when diagnosing and managing thyroid cancer. Our findings can be used to develop decision models that account for competing causes of death, as an aid for clinical decision making.