Real-world validation of the risk estimation of tumor recurrence after transplant (RETREAT) score: Insights from UNOS data on hepatocellular carcinoma recurrence after liver transplant.

4117 Background: For over two decades, established criteria have guided the selection of liver transplantation (LT) candidates in hepatocellular carcinoma (HCC), yet recurrence remains a significant clinical challenge with limited treatment options. The Risk Estimation of Tumor Recurrence After Transplant (RETREAT) score was developed to address this gap. Further validation is needed to confirm its utility in real-world settings. Methods: We conducted a validation study using the United Network for Organ Sharing (UNOS) database to evaluate the predictive performance of the RETREAT score in adult liver transplant recipients with HCC from 2009 to 2024. The analysis included 4,975 patients. Kaplan–Meier survival analysis was performed, and recurrence rates were compared across RETREAT score groups using the log-rank test. The predictive accuracy of the RETREAT score for HCC recurrence was assessed by calculating the concordance index (C-index), area under the ROC curve (AUC) evaluating the model's ability to discriminate between recurrence and non-recurrence events. Results: Among the 4,975 liver transplant recipients with hepatocellular carcinoma (HCC), the distribution of the RETREAT score was as follows: 13 patients (0.26%) had a score of 0, 1,713 patients (34.43%) had a score of 1, 1,981 patients (39.81%) had a score of 2, 524 patients (10.53%) had a score of 3, 526 patients (10.57%) had a score of 4, and 218 patients (4.38%) had a score ≥5. Kaplan–Meier survival analysis demonstrated a significant association between the RETREAT score and HCC recurrence (p < 2e-16). The hazard ratio for recurrence with each unit increase in the RETREAT score was 1.685 (95% CI: 1.574 to 1.803). The model’s predictive accuracy, as assessed by the C-index, was 0.697 (95% CI: 0.668–0.725), and the AUC was 0.684 (95% CI: 0.655–0.713). Conclusions: The RETREAT score demonstrates a C-index of 0.697 in predicting HCC recurrence after liver transplantation. This model offers valuable risk stratification but could benefit from further refinement to improve its predictive accuracy.