Purpose: The study aimed to disclose mortality pattern and quantitatively evaluate risks for cause-specific mortality among thyroid cancer survivors.
Methods: We included 173,710 patients from the Surveillance, Epidemiology, and End Results (SEER) database with thyroid cancer diagnosed between 1975 and 2015. Standardized mortality ratio (SMR) was calculated using general US population as the reference. Cumulative incidence function curves were constructed to elaborate crude cause-specific mortality by histology. Cox proportional hazards regression model was adopted to identify predictors for cause-specific mortality, expressed as hazard ratio (HR) and 95% confidence interval (CI).
Results: After a median follow-up of 101 months, 23,040 (13.3%) deaths occurred, of which 29.1% and 21.7% were attributable to thyroid cancer and cardiovascular disease (CVD), respectively. CVD SMRs were 1.14, 1.47, 1.21, and 5.66 in patients with follicular, Hürthle cell, medullary and anaplastic histology, respectively. The adjusted HRs of thyroid cancer-specific mortality were 1.59 (95% CI: 1.46-1.74), 1.87 (95% CI: 1.65-2.12), 3.66 (95% CI: 3.31-4.05), and 12.65 (95% CI: 11.50-13.92) for follicular, Hürthle cell, medullary, and anaplastic histology, respectively, as compared with papillary histology; HRs of CVD-specific mortality were 1.23 (95% CI: 1.12-1.34), 1.27 (95% CI: 1.11-1.46), 1.13 (95% CI: 0.96-1.33), and 1.60 (95% CI: 1.19-2.16), respectively. Older age, male sex, nonwhite race, unmarried status, and advanced stage were independent predictors of CVD-specific mortality, while receiving surgery and radiotherapy were protective against CVD-specific mortality.
Conclusions: We disclosed distinct mortality patterns by histology and identified predictors of CVD-specific mortality in thyroid cancer survivors, supporting CVD intervention for aggressive thyroid cancer.
Keywords: Cardiovascular disease(s); Competing-risk analysis; Mortality; Survival analysis; Thyroid cancer.