Table 3. Cox multivariate analysis of factors associated with overall survival with and without adjusting for the variables that significantly associated with PD-L1 expression.

Variable	Adjusted for PD-L1-associated variables			Unadjusted for PD-L1-associated variables
	RR	95%CI	P Value	RR	95%CI	P Value
Age	1.776	1.122–2.811	<0.05	1.363	0884–2.102	0.16
Tumor location	0.552	0.346–0.882	<0.05	0.503	0.381–0.796	<0.01
Differentiation grade	0.561	0.314–1.001	<0.05	0.374	0.213–0.656	<0.01
Primary tumor (pT)	1.76	0.839–3.691	0.135	2.351	1.176–4.702	<0.05
Regional lymph node (pN)	1.898	1.186–3.037	<0.01	2.053	1.303–3.236	<0.05
Distant metastasis (pM)	7.808	4.285–14.229	<0.001
Metastatic progression	2.578	1.390–4.782	<0.01
PD-L1 expression index	1.174	0.696–1.979	0.548	2.07	1.342–3.193	<0.01