External Validation of Prognostic Models for Nonmetastatic Clear Cell Renal Cell Carcinoma in a Japanese Cohort: Evaluation of Predictive Performance.

objectivesTo characterize contemporary postoperative outcomes and risk stratification in a large Japanese real-world cohort of patients with clinically nonmetastatic clear cell renal cell carcinoma (ccRCC), and to externally validate commonly used prognostic models.

methodsWe retrospectively analyzed 1677 Japanese patients with clinically nonmetastatic ccRCC who underwent radical or partial nephrectomy between 2010 and 2025. Disease-free survival (DFS) and overall survival (OS) were evaluated. The Leibovich score, SSIGN score, AUA risk groups, and GRANT score were externally validated. Model discrimination was assessed using Harrell's C-index.

resultsDuring a median follow-up of 36 months, 160 patients (9.5%) experienced recurrence and 115 (6.9%) died, including 28 renal cancer-specific deaths. The 3-, 5-, and 10-year DFS rates were 91.2%, 87.6%, and 75.9%, respectively; corresponding OS rates were 95.0%, 91.1%, and 80.9%. Pathological T stage, WHO/ISUP grade, and lymphovascular invasion (LVI) were independently associated with DFS, whereas age, ASA physical status, and LVI were independently associated with OS. All four models significantly stratified DFS and OS. For DFS, the Leibovich score showed favorable discrimination, with a C-index of 0.785 as a continuous score and 0.769 as a risk-group model. In a post hoc exploratory analysis, adding LVI to the Leibovich score slightly increased the C-index for DFS, but the improvement was not statistically significant.

conclusionsEstablished prognostic models consistently stratified recurrence risk in Japanese patients with clinically nonmetastatic ccRCC. The Leibovich score may serve as a useful reference for postoperative risk assessment, whereas the added value of LVI requires further validation.