Data sources
cancer
CANCER
This study combined data from two sources. The data source of this retrospective training and internal validation cohort was from the Surveillance, Epidemiology, and End Results Program (SEER). At present, the SEER database consists of cancer registries from 21 geographic areas, covering approximately one-third of the American population [In addition, data from the Affiliated Hospital of Qingdao University, Qilu Hospital of Shandong University and Shandong Provincial Hospital were used to externally validate the model. According to the prespecified protocol, all medical records were retrieved, and data were extracted by two reviewers to improve the validity. The interrater reliability between the evaluators was found to be excellent (Cohen κ index 0.9). Furthermore, we adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for cohort studies to ensure the quality of the research [