Table 2.

Significant prognostic factors for overall survival in the training set

Characteristics	HR (95% CI)	P-value
Lactate dehydrogenase (U/L)		.015
<245	Reference
≥245	1.491 (1.081–2.057)
No. of metastatic sites		.050
Single	Reference
Multiple	1.429 (1.000–2.047)
Liver metastasis		<.001
No	Reference
Yes	2.319 (1.254–4.291)
Posttreatment EBV DNA		<.001
Undetectable	Reference
Detectable	1.923 (1.406–2.630)
Response of metastasis
Complete response	Reference
Partial response	1.668 (0.839–3.316)	.144
Stable disease	2.813 (1.373–5.762)	.005
Progression disease	6.607 (3.025–14.429)	<.001

Abbreviations: CI = confidence interval; EBV = Epstein—Barr virus; HR = hazard ratio.

Variables with a P < .1 in the univariate analyses were entered into a stepwise multivariate Cox regression analysis. Model selection was made based on a stepwise method using the Akaike information criterion as a stop rule. The Akaike information criterion of the final model was 1838.2.