Assessment of Survival Model Performance Following Inclusion of Epstein-Barr Virus DNA Status in Conventional TNM Staging Groups in Epstein-Barr Virus–Related Nasopharyngeal Carcinoma

IMPORTANCE: Nonanatomic prognostic factors complement the traditional anatomic staging system and could be incorporated into the tumor-node-metastasis (TNM) framework. Several diseases have incorporated nonanatomic prognostic factors into the determination of TNM staging groups. OBJECTIVE: To refine TNM staging groups for Epstein-Barr virus (EBV)–related nonmetastatic nasopharyngeal carcinoma (NPC) by incorporating EBV DNA status. DESIGN, SETTING, AND PARTICIPANTS: This multicenter prognostic study included patients with NPC treated with radiotherapy at 2 hospitals in China from January 2008 to December 2016. Progression-free survival and overall survival according to EBV DNA status and the TNM staging system were compared. Recursive partitioning analysis (RPA) combined with supervised clustering was applied to derive prognostic groupings, and then a refined RPA staging schema was developed, validated, and compared with existing staging schemes. Statistical analyses were conducted from October 1, 2020, to June 15, 2021. EXPOSURES: Curative intensity-modulated radiotherapy with or without platinum-based chemotherapy. MAIN OUTCOMES AND MEASURES: The primary end point was progression-free survival. The performance of the staging system was assessed using the time-dependent area under the receiver operating characteristic curves and the TNM stage system’s evaluation methodology. RESULTS: A total of 2354 patients (1709 men [72.6%]; median [interquartile range] age, 45 [38-53] years) were split into training (1372 [58.3%]), internal validation (672 [28.5%]), and external validation (310 [13.2%]) cohorts. Pretreatment EBV DNA was detected in 1338 (56.8%) patients. EBV DNA status was an independent prognostic factor: lower survival probability by higher TNM stage was evident in EBV DNA–positive patients but not in those with EBV DNA–negative disease. After integrating EBV DNA status and TNM stage, nonmetastatic NPC cases were categorized into RPA-I (T1-3N0 or EBV DNA–negative T1-3N1 cancers), RPA-II (EBV DNA–positive T1-3N1-2 or EBV DNA–negative T1-3N2-3/T4N0-3 cancers), and RPA-III (EBV DNA–positive T4N0-3/T1-3N3 cancers) groups, each with distinctly different prognosis. This system of RPA staging outperformed the current TNM stage system and 2 reported RPA staging schemes. These results were internally and externally validated. CONCLUSIONS AND RELEVANCE: An RPA-based staging system for EBV-related NPC cases was associated with improved outcomes. This staging system may facilitate prognostic stratification and clinical trial designs.