Table 2.

Stratified models for PFS and OS of individual IPI risk factors

Risk factor	PFS				OS
	Univariate analysis		Multivariate analysis		Univariate analysis		Multivariate analysis
	Hazard ratio (95% CI)	P value	Hazard ratio (95% CI)	P value	Hazard ratio (95% CI)	P value	Hazard ratio (95% CI)	P value
Age, y
≤60	Reference	< .0001	Reference	< .0001	Reference	< .0001	Reference	< .0001
>60	1.615 (1.393-1.872)		1.400 (1.206-1.626)		2.008 (1.682-2.398)		1.760 (1.472-2.104)
Ann Arbor stage
Ⅰ-Ⅱ	Reference	< .0001	Reference	< .0001	Reference	< .0001	Reference	< .0001
Ⅲ-Ⅳ	3.157 (2.689-3.707)		2.083 (1.730-2.507)		3.703 (3.032-4.522)		2.228 (1.775-2.797)
Extranodal involvement
0-1	Reference	< .0001	Reference	.029	Reference	< .0001	Reference	.073
≥ 2	2.288 (1.965-2.664)		1.209 (1.020-1.433)		2.433 (2.036-2.908)		1.197 (0.984-1.456)
Serum LDH
Normal	Reference	< .0001	Reference	< .0001	Reference	< .0001	Reference	< .0001
>1 × ULN	2.928 (2.506-3.421)		1.960 (1.656-2.320)		3.765 (3.100-4.574)		2.416 (1.960-2.979)
ECOG performance status
0-1	Reference	< .0001	Reference	< .0001	Reference	< .0001	Reference	< .0001
≥2	2.721 (2.260-3.277)		1.712 (1.414-2.074)		3.159 (2.563-3.894)		1.888 (1.523-2.341)

N = 1932

CI, confidence interval; ULN, upper limit of normal.