Development and Validation of Nomograms for Predicting Cancer-Specific Survival in Elderly Patients with Intrahepatic Cholangiocarcinoma After Liver Resection: A Competing Risk Analysis.

Background: There are few studies on the prognosis of elderly intrahepatic cholangiocarcinoma (iCCA) patients after liver resection. The aims of this study were to assess the cumulative incidences of cancer-specific mortality in elderly iCCA patients and to construct a corresponding competing risk nomogram for elderly iCCA patients. Methods: We performed a retrospective analysis of elderly patients with iCCA who underwent liver resection between January 2006 and December 2019. Eligible elderly iCCA patients were randomly divided into training and validation sets at a ratio of 7:3. Based on the results of multivariate analysis using the Fine-Gray competing risk model, we developed a competing risk nomogram using data from the training set to predict the cumulative probabilities of iCCA-specific mortality. The performance of the nomogram was measured by the concordance index (C-index) and calibration curves. To evaluate the clinical usefulness of the nomogram, the clinical benefit was measured by using decision curve analysis (DCA). Furthermore, the patients were categorized into two groups according to the dichotomy values of the nomogram-based scores, and their survival differences were assessed using Kaplan-Meier and cumulative incidence function (CIF) curves. Results: The 1-year, 3-year and 5-year cumulative iCCA-specific mortalities were 19.7%, 48.3% and 56.1%, respectively, for elderly iCCA patients. The multivariate Fine-Gray analysis indicated that microvascular invasion, macroscopic vascular invasion and lymph node metastasis were related to a significantly higher likelihood of iCCA specific mortality. The established nomogram was well calibrated and had a good discriminative ability, with a concordance index (C-index) of 0.742 (95% CI, 0.708-0.748). Furthermore, the DCA indicated that the nomogram had positive net benefits compared with the conventional staging systems. In the training set and validation sets, the high-risk group had the higher probabilities of iCCA cancer-specific mortality than the low-risk group; meanwhile, the patients in the high-risk the group had significantly poorer overall survival (OS) than those in the low-risk group. Conclusion: Elderly iCCA patients had comparable long-term outcomes with non-elderly iCCA patients. In addition, we constructed a prognostic nomogram for predicting survival in elderly iCCA patients based on the competing risk analysis. The competing risk nomogram displayed excellent discrimination and calibration.