Data collection and selection criteria
PRIMARY CANCER
We used SEER*Stat version 8.3.9 software (accession number: 10248‐Nov2020) to retrieve patients' data that were further extracted based on the following criteria: (1) aged over 18 years old, (2) histopathologic diagnosis of CC between 2004 and 2016, and (3) primary stage of diagnosis (I‐IVA) of CC, with complete data about survival information, which incorporated survival months and status of survival (alive recorded as 0 or dead recorded as (1). The exclusion criteria were built based on the following parameters: (1) patients who had more than one primary cancer, (2) missing information on survival time (Illustration of the patient selection flowchart.