Prognostic value of prior malignancy history in stage I differentiated thyroid cancer: a SEER-based study.Background
 Stage I DTC patients were identified from the Surveillance, Epidemiology, and End Results (SEER) database. 
SEER
The Kaplan-Meier method and Cox proportional hazards regression method were used to determine the risk factors for overall survival (OS) and disease-specific survival (DSS). 
Kaplan-Meier method
The Kaplan-Meier method and Cox proportional hazards regression method were used to determine the risk factors for overall survival (OS) and disease-specific survival (DSS). 
Cox proportional hazards regression method
A competing risk model was also used to determine the risk factors for DTC-related death after considering the competitive risks.  In the competing risk model, in the multivariate analysis, prior malignancy history was a risk factor for the DTC-related deaths [subdistribution HR (SHR) =4.32, 95% CI: 2.233-8.3593, P<0.001] after considering the competitive risks. 
competing risk model
In addition, conditional survival analysis in patients with stage I DTC was performed.



conditional survival analysis