Table 1. Patient and disease characteristics.

Parameter	EBV DNA ≥ 4000 copies/ml		EBV DNA < 4000 copies/ml		P value
	No. of patients	%	No. of patients	%
	648		819
Age (years)					0.068
Range	11–96		11–94
Median	46		45
Sex					0.132
Male	474	73.1	568	69.4
Female	174	26.9	251	30.6
ECOG					0.660
≤ 1	645	99.5	817	99.8
> 1	3	0.5	2	0.2
WHO classification					0.342
II	29	4.5	46	5.6
III	619	95.5	773	94.4
T classification					< 0.001
T1–2	125	19.3	282	34.4
T3–4	523	80.7	537	65.6
N classification					< 0.001
N0–1	253	39.0	541	66.1
N2–3	395	61.0	278	33.9
Overall stage*					< 0.001
I	3	0.5	57	7.0
II	30	4.6	143	17.5
III	341	52.6	452	55.2
IVa–b	274	42.3	167	20.4
Treatment strategy					< 0.001
CRT¶	547	84.4	578	70.6
RT#	101	15.6	241	29.4
Follow-up time, months
Median	44		48
Range	1–85		1–103		0.002

Abbreviations: WHO, World Health Organization; ECOG, Eastern Cooperative Oncology Group; 2D-RT, two-dimensional radiotherapy; IMRT, intensity-modulated radiotherapy; DM, distant metastasis;

^¶CRT, chemoradiotherapy with or without sequential chemotherapy (induction or adjuvant).

^#RT, radiotherapy with or without sequential chemotherapy (induction or adjuvant).

^*The 7th AJCC/UICC staging system.