Table 2.

Clinical characteristics of study participants

Prognostic factor	3-year LRRFS	χ2	Pa	3-year DMFS	χ2	Pa	3-year FFS	χ2	Pa	3-year OS	χ2	Pa
Gender		2.977	0.084		2.245	0.134		5.094	0.024		1.091	0.296
Male	82.9			88.5			72.9			89.5
Female	89.3			94.2			83.7			96.3
Age		1.414	0.234		0.209	0.648		0.544	0.461		2.276	0.131
≤ 65	85.6			89.7			76.4			91.7
> 65	72.3			94.7			68.2			84.4
Plasma EBV-DNA (copies/mL)		0.384	0.536		0.001	0.976		0.124	0.725		0.776	0.378
≤ 500	83.0			90.6			75.3			90.0
> 500	87.7			88.5			76.4			93.6
T category		0.013	0.911		0.707	0.401		0.587	0.444		0.069	0.793
T 1–2	82.0			93.1			78.7			91.0
T 3–4	85.2			89.4			75.3			91.4
N category		1.449	0.229		0.235	0.628		1.994	0.158		0.226	0.634
N 0–1	87.9			90.2			79.5			92.3
N 2–3	83.0			89.9			73.8			90.7
Stage		0.238	0.626		2.024	0.155		1.922	0.166		1.184	0.277
III	85.7			91.4			78.2			93.3
IVA	83.3			88.7			73.2			88.9
Time to boost after radiotherapy (days)		1.077	0.584		1.749	0.417		0.902	0.637		0.432	0.806
1–14	92.0			81.6			73.8			90.0
15–28	88.8			90.5			79.7			95.4
> 28	81.2			92.4			75.0			90.2
Sites of residual		3.533	0.171		8.580	0.014		4.181	0.124		12.631	0.002
Primary focus	79.4			98.8			78.2			94.5
Lymph nodes	90.2			87.4			78.4			92.4
Primary focus + lymph nodes	76.2			77.7			57.6			75.9

Statistically significant value is shown in bold

DMFS distant metastasis-free survival, EBV-DNA Epstein-Barr virus-deoxyribonucleic acid, FFS failure-free survival, LRRF locoregional relapse-free survival, OS overall survival

^aLog-rank test