Table S4. Stratified univariable Cox regression analysis of radiomics index.

Variables	Training cohort			Validation cohort
	HR (95% CI)	P		HR (95% CI)	P
KPS, Karnofsky performance status; LN, lymph node; cTNM, clinical TNM stage; pTNM, pathological TNM stage.
Age (year)
<65	3.28 (2.41−4.47)	<0.001		2.56 (1.56−4.21)	<0.001
≥65	4.42 (2.65−7.35)	<0.001		3.76 (1.79−7.92)	<0.001
Gender
Male	3.50 (2.61−4.70)	<0.001		2.78 (1.75−4.42)	<0.001
Female	2.68 (1.33−5.44)	0.006		3.43 (1.26−9.33)	0.016
KPS
90−100	3.72 (2.65−5.23)	<0.001		3.16 (1.91−5.22)	<0.001
70−80	3.31 (2.17−5.04)	<0.001		2.49 (1.19−5.22)	0.016
Differentiation
G1	5.80 (3.10−10.87)	<0.001		8.92 (1.96−40.60)	0.005
G2	5.07 (3.14−8.19)	<0.001		2.85 (1.61−5.05)	<0.001
G3	2.38 (1.66−3.41)	<0.001		2.42 (1.30−4.52)	0.005
Tumor location
Upper	4.00 (2.42−6.61)	<0.001		3.14 (1.53−6.43)	0.002
Middle	3.61 (2.51−5.21)	<0.001		3.74 (1.96−7.11)	<0.001
Lower	2.83 (1.56−5.12)	<0.001		2.29 (0.93−5.64)	0.072
Surgical margin
R0	3.40 (2.59−4.46)	<0.001		2.96 (1.94−4.50)	<0.001
R1/2	6.29 (1.92−20.61)	0.002		3.02 (0.35−26.09)	0.314
Vascular invasion
No	3.50 (2.57−4.76)	<0.001		2.93 (1.87−4.61)	<0.001
Yes	3.07 (1.88−5.03)	<0.001		3.33 (1.08−10.24)	0.036
Neural invasion
No	3.44 (2.58−4.60)	<0.001		3.42 (2.09−5.59)	<0.001
Yes	4.07 (2.12−7.82)	<0.001		1.68 (0.75−3.78)	0.208
Resected LN number
<20	2.91 (1.97−4.28)	<0.001		3.29 (1.82−5.94)	<0.001
≥20	4.33 (3.01−6.23)	<0.001		2.78 (1.53−5.07)	<0.001
cTNM (8th)
I−II	2.55 (1.57−4.14)	<0.001		2.13 (0.99−4.58)	0.053
III−IVA	4.62 (3.31−6.45)	<0.001		3.94 (2.34−6.65)	<0.001
pTNM (8th)
I−II	2.37 (1.34−4.18)	0.003		2.16 (0.95−4.92)	0.067
III−IVA	2.60 (1.91−3.54)	<0.001		2.30 (1.41−3.75)	<0.001