The effects of radiotherapy and prognostic nomogram for pancreatic cancer patients with liver-only metastases

Background: This study aimed to investigate the effect of radiotherapy on pancreatic cancer patients with liver metastasis only, and to establish a prognostic model. Methods: Pancreatic cancer patients with liver-only metastases were obtained from 2010 to 2019 in the Surveillance, Epidemiology, and End Results (SEER) database. Then they were divided into a radiotherapy group and a non-radiotherapy group. Cancer-specific survival (CSS) before and after propensity score matching(PSM) was compared between the two groups. The radiotherapy group was then divided into training and validation cohorts. The prognostic nomogram for 6-, and 12-mouth CSS was constructed based on the training set. In addition, 38 patients were recruited from our hospital as an external validation set. The calibration curves, receiver operating characteristic (ROC) curve, Harrell’s concordance index (C-index), decision curve analysis (DCA), and Kaplan-Meier analysis based on risk stratification were performed to evaluate and verify this model. Results: A total of 17453 patients with hepatic oligometastatic pancreatic cancer were included, of which 622 ( 3.6 % ) received radiotherapy and 16831 ( 96.4 % ) did not. Radiotherapy can significantly prolong survival time [median CSS: 8 months vs 5 months (HR, 0.716; 95%CI=0.655–0.783; p <0.001)]. After PSM, similar results can be obtained [median CSS: 8 months vs 7 months (HR, 0877; 95% CI=0.772–0.997; P=0.045)]. Independent prognostic factors in radiotherapy patients included age, race, histology, N staging, surgery, and chemotherapy. The ROC, C-index and Calibration curves showed good discrimination and calibration. DCA and KM curves further demonstrated the model's clinical applicability. Conclusion: Radiotherapy significantly improves survival compared to non-radiotherapy. Patients younger than 70 years old, non-black, with no lymph node metastasis, primary tumor surgery, and systemic chemotherapy have better prognosis. Finally, we developed and validated a model for prognostication and patient counseling.