The addition of pretreatment plasma Epstein–Barr virus DNA into the eighth edition of nasopharyngeal cancer TNM stage classification

Abstract

The eighth edition of the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) stage classification (TNM) for nasopharyngeal carcinoma (NPC) was launched. It remains unknown if incorporation of nonanatomic factors into the stage classification would better predict survival. We prospectively recruited 518 patients with nonmetastatic NPC treated with radical intensity‐modulated radiation therapy ± chemotherapy based on the eighth edition TNM. Recursive partitioning analysis (RPA) incorporating pretreatment plasma Epstein–Barr virus (EBV) DNA derived new stage groups. Multivariable analyses to calculate adjusted hazard ratios (AHRs) derived another set of stage groups. Five‐year progression‐free survival (PFS), overall survival (OS) and cancer‐specific survival (CSS) were: Stage I (PFS 100%, OS 90%, CSS 100%), II (PFS 88%, OS 84%, CSS 95%), III (PFS 84%, OS 84%, CSS 90%) and IVA (PFS 71%, OS 75%, CSS 80%) (p < 0.001, p = 0.066 and p = 0.002, respectively). RPA derived four new stages: RPA‐I (T1–T4 N0–N2 & EBV DNA <500 copies per mL; PFS 94%, OS 89%, CSS 96%), RPA‐II (T1–T4 N0–N2 & EBV DNA ≥500 copies per mL; PFS 80%, OS 83%, CSS 89%), RPA‐III (T1–T2 N3; PFS 64%, OS 83%, CSS 83%) and RPA‐IVA (T3–T4 N3; PFS 63%, OS 60% and CSS 68%) (all with p < 0.001). AHR using covariate adjustment also yielded a valid classification (I: T1–T2 N0–N2; II: T3–T4 N0–N2 or T1–T2 N3 and III: T3–T4 N3) (all with p < 0.001). However, RPA stages better predicted survival for PS and CSS after bootstrapping replications. Our RPA‐based stage groups revealed better survival prediction compared to the eighth edition TNM and the AHR stage groups.