Calibration curves in the training cohort and validation cohort. A–C Nomogram calibration curves for predicting OS in advanced PBTC patients at 1, 3, and 5 years in the training cohort. D–F Nomogram calibration curves predicting the OS for advanced PBTC patients at years 1, 3, and 5 in the validation cohort. The red line represents an equal probability of observed and predicted values. OS: overall survival; PBTC: pancreatic body tail cancer.