Table 1

Multivariate risk models and bootstrap validation

Covariate	With PD-L1 expression				Bootstrap means
Covariate	N	HR	95% CI	P value	HR	95% CI
ECOG PS				<0.001
0	352	1			1
≥1	476	1.9	1.55 to 2.33		1.92	1.6 to 2.36
Hemoglobin				0.001
≥10 g/L	695	1			1
<10 g/L	133	1.49	1.18 to 1.88		1.53	1.19 to 1.98
Liver metastases				<0.001
No	603	1			1
Yes	225	1.8	1.47 to 2.19		1.8	1.45 to 2.28
Time from last chemotherapy				0.001
>6 months	323	1			1
≤6 months	505	1.41	1.16 to 1.72		1.42	1.14 to 1.76
NLR>5				<0.001
No	561	1			1
Yes	267	1.93	1.59 to 2.35		1.96	1.56 to 2.43
PD-L1 expression				0.006
IC2/3	238	1			1
IC0/1	590	1.35	1.09 to 1.67		1.38	1.12 to 1.73
Alkaline phosphatase				<0.001
Low/normal	634	1			1
High	194	1.7	1.38 to 2.09		1.78	1.4 to 2.28
Bone metastases				0.037
No	616	1
Yes	212	1.24	1.01 to 1.52
TNM at diagnosis				0.049
0, I, II	294	1
III, IV	534	1.22	1.001 to 1.48
ECOG PS				<0.001
0	373	1			1
≥1	515	1.83	1.5 to 2.24		1.82	1.52 to 2.22
Hemoglobin				<0.001
≥10 g/L	745	1			1
<10 g/L	143	1.61	1.28 to 2.02		1.61	1.25 to 2.14
Liver metastases				<0.001
No	643	1			1
Yes	245	1.87	1.54 to 2.26		1.88	1.54 to 2.32
Time from last chemotherapy				0.001
>6 months	347	1			1
≤6 months	541	1.39	1.15 to 1.68		1.4	1.14 to 1.71
NLR>5				<0.001
No	602	1			1
Yes	286	1.79	1.48 to 2.17		1.8	1.43 to 2.22
Bone metastases				0.004
No	660	1			1
Yes	228	1.33	1.1 to 1.62		1.33	1.08 to 1.62
Alkaline phosphatase				<0.001
Low/normal	676	1			1
High	212	1.67	1.37 to 2.04		1.7	1.37 to 2.17

ECOG PS, Eastern Cooperative Oncology Group performance status; ICs, immune cells; NLR, neutrophil-to-lymphocyte ratio; OS, overall survival; TNM, tumor–node–metastases.