<i>Baseline characteristics of the validation cohort</i>

Clinical and pathological data of CRCLM patients who underwent primary tumor resection and chemotherapy from 2010 to 2015 were extracted from the SEER 8 registries database (SEER*Stat 8.4.3). A total of 3252 cases met the inclusion and exclusion criteria. Continuous variables were converted to categorical variables using X-tile software, which also determined optimal cutoff values for grouping. Patients were randomly divided into a training cohort (n=2276) and a validation cohort (n=976) in a 7:3 ratio.