Development and validation of a prognostic nomogram for unresectable pancreatic ductal adenocarcinoma with synchronous liver metastases: a study based on the SEER database and an external cohort.

BACKGROUND

Pancreatic ductal adenocarcinoma with synchronous liver metastases (PDACLM) represents a highly aggressive malignancy with limited treatment options and poor prognosis. While conversion therapy may enable curative surgery in a small subset of patients, the majority ultimately remain ineligible for resection. Prognostic tools tailored to this unresected population are lacking but urgently needed for guiding clinical decisions.

METHODS

We conducted a retrospective cohort study using 9,469 patients with histologically confirmed PDACLM from the SEER database (2010-2015), supplemented by an external validation cohort of 94 patients treated at the Second Affiliated Hospital of Chongqing Medical University (2020-2023). Multivariate Cox regression analysis was used to identify independent prognostic factors. A nomogram was constructed and validated internally and externally to predict individualized overall survival (OS) at 12, 18, and 24 months.

RESULTS

Age ≥65 years, higher tumor grade, and undetermined nodal status were independently associated with reduced OS, while chemotherapy, radiotherapy, and metastasis-directed surgery significantly improved survival outcomes (all P<0.05). The nomogram demonstrated good discriminative performance with a C-index of 0.73 in the training cohort and 0.72 in internal validation. External validation showed consistent predictive accuracy (C-index: 0.715). Calibration plots and decision curve analyses supported the model's reliability and clinical utility.

CONCLUSION

We developed and externally validated a clinically accessible nomogram for survival prediction in unresected PDACLM patients. This tool may assist clinicians in risk stratification and treatment planning for a frequently overlooked patient subgroup. Further prospective validation is warranted to confirm its applicability in broader clinical settings.