Table 1. Univariate and multivariate survival analysis of three cohorts.

Variable	Discovery cohort					Validation-1 cohort					Validation-2 cohort
	Univariate analysis			Multivariate analysis		Univariate analysis			Multivariate analysis		Univariate analysis			Multivariate analysis
	N	P-value	HR(95%CI)	P-value a	HR(95%CI) a	N	P-value	HR(95%CI)	P-value b	HR(95%CI) b	N	P-value	HR(95%CI)	P-value c	HR(95%CI) c
AJCC stage
I/IIA	26		Ref		Ref	48		Ref		Ref	14		Ref		Ref
IIB/III/IV	71	0.038	1.79(1.07-3.00)	0.138	1.57(0.86-2.86)	124	0.013	1.89(1.22-2.93)	0.908	1.07(0.33-3.51)	52	0.125	1.69(0.92-3.09)	0.064	3.36(0.93-12.13)
T stage
T1/T2	18		Ref		Ref	31		Ref		Ref	NA
T3/T4	80	0.863	0.95(0.51-1.76)	0.209	1.55(0.78-3.06)	143	0.022	2.04(1.24-3.34)	0.413	1.34(0.67-2.68)	NA	NA	NA	NA	NA
N stage
N0	28		Ref		Ref	48		Ref		Ref	20		Ref		Ref
N+	73	0.027	1.80(1.09-2.95)	0.138	1.57(0.86-2.86)	123	0.006	2.03(1.31-3.15)	0.402	1.63(0.52-5.15)	46	0.296	1.38(0.77-2.47)	0.564	0.73(0.26-2.10)
Histological grade
G1/G2	NA					125		Ref		Ref	34		Ref		Ref
G3/G4	NA	NA	NA	NA	NA	50	0.064	1.50(0.94-2.40)	0.339	1.24(0.80-1.93)	31	0.018	1.87(1.05-3.32)	0.272	3.25(0.40-26.69)
Risk score
low risk	50		Ref		Ref	88		Ref		Ref	33		Ref		Ref
high risk	51	<0.0001	2.53(1.53-4.17)	0.022	1.82(1.09-3.05)	89	0.0006	2.05(1.36-3.09)	0.023	1.67(1.07-2.60)	33	0.038	1.79(1.02-3.12)	0.009	2.29(1.23-4.24)

Abbreviation: N, number; HR, hazard ratio; CI, confidence interval; Ref, reference; AJCC, American Joint Committee on Cancer; NA, not available.

^a multivariate analysis was adjusted by AJCC stage, T stage, N stage

^b multivariate analysis was adjusted by AJCC stage, T stage, N stage, Histological grade

^c multivariate analysis was adjusted by AJCC stage, N stage, Histological grade