Table 1_Development and external validation of a nomogram to predict survival and guide surgical strategy for colorectal cancer with synchronous liver and lung metastases: a SEER-based analysis.docx

We aimed to develop and externally validate a nomogram for overall survival (OS) prediction and to explore its potential value in guiding selection for primary tumor resection (PTR). Patients diagnosed with CRC-SLLM between 2010 and 2015 were identified from the Surveillance, Epidemiology, and End Results (SEER) database and randomly assigned to a training cohort (n = 808) and an internal validation cohort (n = 345) in a 7:3 ratio, whereas external validation was performed using 65 patients from the Fourth Hospital of Hebei Medical University, China.

After feature selection with least absolute shrinkage and selection operator (LASSO) regression, a multivariable Cox-based nomogram was constructed, and its performance was assessed using time-dependent receiver operating characteristic curves, calibration plots, decision curve analysis (DCA), and risk stratification. The final nomogram incorporated nine predictors: age, primary tumor site, histological grade, tumor size, N stage, bone metastasis, carcinoembryonic antigen status, metastasectomy, and chemotherapy.