Disease-Specific Mortality of Differentiated Thyroid Cancer Patients in Korea: A Multicenter Cohort Study

Background: Little is known regarding disease-specific mortality of differentiated thyroid cancer (DTC) patients and its risk factors in Korea. Methods: We retrospectively reviewed a large multi-center cohort of thyroid cancer from six Korean hospitals and included 8,058 DTC patients who underwent initial surgery between 1996 and 2005. Results: Mean age of patients at diagnosis was 46.2 +/- 12.3 years; 87% were females. Most patients had papillary thyroid cancer (PTC; 97%) and underwent total thyroidectomy (85%). Mean size of the primary tumor was 1.6 +/- 1.0 cm. Approximately 40% of patients had cervical lymph node (LN) metastases and 1.3% had synchronous distant metastases. During 11.3 years of follow-up, 150 disease-specific mortalities (1.9%) occurred; the 10-year disease-specific survival (DSS) rate was 98%. According to the year of diagnosis, the number of disease-specific mortality was not different. However, the rate of disease-specific mortality decreased during the study period (from 7.7% to 0.7%). Older age (>= 45 years) at diagnosis, male, follicular thyroid cancer (FTC) versus PTC, larger tumor size (>2 cm), presence of extrathyroidal extension (ETE), lateral cervical LN metastasis, distant metastasis and tumor node metastasis (TNM) stage were independent risk factors of disease-specific mortality of DTC patients. Conclusion: The rate of disease- specific mortality of Korean DTC patients was 1.9%; the 10-year DSS rate was 98% during 1996 to 2005. Older age at diagnosis, male, FTC, larger tumor size, presence of ETE, lateral cervical LN metastasis, distant metastasis, and TNM stages were significant risk factors of disease- specific mortality of Korean DTC patients.