Table 2. Survival comparisons between among subgroups.
| Stratification | OS | PFS | DMFS | LRFS | ||||
|---|---|---|---|---|---|---|---|---|
| 5 year (%) | P value | 5 year (%) | P value | 5 year (%) | P value | 5 year (%) | P value | |
| I vs. II–III low EBV DNA | 100% vs. 94.7% | 0.106 | 100% vs.87.2% | 0.013 | 100% vs. 93.5% | 0.056 | 100% vs. 93.8% | 0.080 |
| I vs. IVa–b low EBV DNA | 100% vs. 92.9% | 0.041 | 100% vs. 89.0% | 0.010 | 100% vs. 92.4% | 0.033 | 100% vs. 96.3% | 0.133 |
| I vs. II–IVa–b low EBV DNA | 100% vs. 94.3% | 0.094 | 100% vs. 89.2% | 0.015 | 100% vs. 93.2% | 0.055 | 100% vs. 94.4% | 0.097 |
| II–III low EBV DNA vs. IVa–b low EBV DNA | 94.7% vs. 92.9% | 0.141 | 87.2% vs. 89.0% | 0.685 | 93.5% vs. 92.4% | 0.394 | 93.8% vs. 96.3% | 0.523 |
| II–III high EBV DNA vs. IVa–b low EBV DNA | 82.7% vs. 92.9% | 0.025 | 70.7% vs. 89.0% | < 0.001 | 79.6% vs. 92.4% | 0.001 | 89.3% vs. 96.3% | 0.022 |
| II–III high EBV DNA vs. IVa–b high EBV DNA | 82.7% vs. 71.7% | 0.001 | 70.7% vs. 66.2% | 0.047 | 79.6% vs. 74.8% | 0.066 | 89.3% vs. 87.6% | 0.425 |
Abbreviations: OS, overall survival; PFS, progression-free survival; DMFS, distant failure-free survival; LRFS, locoregional failure-free survival.
All the 5 year survival rates were calculated using the Kaplan-Meier method.
EBV DNA level was defined as high EBV DNA with concentrations greater than or equal to 4000 copies/ml and low EBV DNA with concentrations smaller than 4000 copies/ml.
P values achieved between different subgroups.