Epstein–Barr virus DNA change level combined with tumor volume reduction ratio after inductive chemotherapy as a better prognostic predictor in locally advanced nasopharyngeal carcinoma

BACKGROUND: To explore the prognosis predicting ability of the combined factors, Epstein–Barr virus DNA change level (EBVCL) and tumor volume reduction ratio (TVRR) after inductive chemotherapy (IC), in locally advanced nasopharyngeal carcinoma (LANPC). METHODS: From 2010 to 2018, 299 LANPC patients were included in this retrospective study. Receiver operating characteristic (ROC) curve analysis was performed to acquire the best critical values. According to the best critical values of EBVCL and TVRR, patients were stratified into low‐ and high‐risk groups. Kaplan–Meier and ROC curve analyses were utilized to verify the prognostic ability of the new predictor (EBVCL+TVRR). The prognostic values among EBVCL+TVRR, EBVCL, TVRR, TNM stage, and the RECIST 1.1 criteria were compared by ROC curve. The primary end points were overall survival (OS), progression‐free survival (PFS), distant metastasis‐free survival (DMFS), and locoregional failure‐free survival (LRFFS). RESULTS: ROC curve analyses of TVRR on three‐year survival showed the best critical values of TVRR was 32.72% for OS, 30.21% for PFS and LRFFS, 29.87% for DMFS. The best critical value of EBVCL was 127 copies/ml for OS, and 87.7 copies/ml for PFS, DMFS, and LRFFS. The three‐year OS, PFS, DMFS, and LRFFS for low‐ and high‐risk groups were 97.7% versus 78.3% (hazard ratio [HR] = 0.2398; 95% confidence interval [CI]: 0.1277–0.4502; p < 0.0001), 91.1% versus 60.9% (HR = 0.3294; 95% CI: 0.2050–0.5292; p < 0.0001), 94.2% versus 68.7% (HR = 0.2413; 95% CI: 0.1284–0.4535; p < 0.0001) and 97.8% versus 77.9% (HR = 0.3078; 95% CI: 0.1700–0.5573; p = 0.0001), respectively. The maximal area under ROC curve of EBVCL+TVRR, EBVCL, TVRR, TNM stage, and RECIST 1.1 criteria for three‐year OS was 0.829, 0.750, 0.711, 0.555, and 0.605, respectively. CONCLUSION: The new‐developed indicator (EBVCL+TVRR) could better predict the LANPC patient's survival after IC compared with TNM stage system or RECIST 1.1 criteria.