Table 2.

Uni- and multivariable Cox regression analyses for DFS in the discovery cohort and validation cohort

Variables	Discovery cohort					Validation cohort
	Univariable analysis		Multivariable analysisa			Univariable analysis		Multivariable analysisa
	Unadjusted HRb (95% CI)	P	Adjusted HRc (95% CI)	P		Unadjusted HRb (95% CI)	P	Adjusted HRc (95% CI)	P
Age at surgery (years)
≥ 65 vs. < 65	1.13 (0.70–1.82)	0.624				1.00 (0.58–1.73)	0.991
Sex
Female vs. male	0.63 (0.39–1.03)	0.067				0.58 (0.36–0.94)	0.026
Smoking status
Former/current vs. never	1.08 (0.66–1.78)	0.748				1.18 (0.76–1.84)	0.469
TNM stage
Stage II vs. stage I	3.82 (1.99–7.34)	< 0.001	2.41 (1.13–5.18)	0.024		2.95 (1.68–5.18)	< 0.001	2.87 (1.64–5.06)	< 0.001
Stage III vs. stage I	5.69 (3.33–9.73)	< 0.001	2.84 (1.33–6.06)	0.007		3.62 (2.15–6.09)	< 0.001	3.23 (1.91–5.48)	< 0.001
Differentiation grade
G3/G4 vs. G1/G2	2.79 (1.72–4.52)	< 0.001	1.68 (1.01–2.82)	0.047		1.56 (1.00–2.43)	0.050
Surgical resection
Limited resection vs. lobectomy/pneumonectomy	1.37 (0.63–2.99)	0.429				1.56 (0.49–4.94)	0.451
Adjuvant chemotherapy
Yes vs. no	3.83 (2.38–6.15)	< 0.001	1.77 (0.91–3.41)	0.090		2.23 (1.35–3.68)	0.002
I-score (three-category)
Intermediate vs. low	0.79 (0.42–1.46)	0.447				1.05 (0.57–1.96)	0.867
High vs. low	0.44 (0.25–0.78)	0.005				0.49 (0.26–0.93)	0.029
I-score (two-category)
High vs. low	0.51 (0.32–0.81)	0.004	0.57 (0.36–0.92)	0.022		0.47 (0.30–0.75)	0.001	0.54 (0.33–0.86)	0.010

Data in parentheses are 95% confidence intervals

DFS  disease-free survival, HR hazard ratio, CI  confidence interval

^aVariables that reach statistical significance at P < 0.10 in the univariable analysis (sex, TNM stage, differentiation grade, adjuvant chemotherapy, two-category I-score) are included in the multivariable analysis

^bThe unadjusted hazard ratios (HR) and P-values are determined by univariable Cox regression analyses

^cThe adjusted hazard ratios (HR) and P-values are determined by multivariable Cox regression analyses