Cohort definition and variables
tumor
TUMOR
We randomly classified the study sample into the training and validation cohorts using a 7:3 ratio. The training and validation cohorts were used to construct and verify the model, respectively. Fourteen variables from the SEER database were included in the study model, including demographic variables (age at diagnosis, sex, race, and marital status), tumor characteristics (laterality, TNM stage, grade, tumor size, and primary site), and treatment status (chemotherapy, surgery, and radiotherapy). Based on the age at diagnosis and tumor size, X-tile software (