Table 1.

Characteristics of included studies.

	Author	Year published	Country	Tumor type	Sample size	Stage	Age (median)	Male (%)	Treatment	Follow-up (months, median)	Endpoint	Cut-off value (high expression)
17	Zhao JP	2021	China	ICCA	468	NR	58	60.30%	Surgery	NR	OS	NLR ≥ 3
18	Ma B	2021	China	ICCA	174	I–IV	58	55.90%	Surgery	25.1	OS/DFS	NLR ≥ 3
19	Zhang ZY	2020	China	ICCA	128	I–III	56	55.00%	Surgery	NR	OS/DFS	NLR ≥ 3
20	Tsilimigras DI	2020	USA	ICCA	688	I–III	57	60.50%	Surgery	22.3	OS	NLR ≥ 5
21	Ohira M	2020	Japan	ICCA	52	I–IV	58	78.84%	Surgery	NR	OS	NLR ≥ 1.93
22	Ji F	2020	China	ECCA	59	I–IV	57	55.93%	Surgery	NR	OS	NLR ≥ 2.93
23	Huh G	2020	Korea	ICCA	137	III–IV	64	60.60%	Non-surgery	9.9	OS/DFS	NLR ≥ 5
24	Filippi L	2020	Latina	ICCA	20	NR	65	45.00%	Non-surgery	12.5	OS	NLR ≥ 2.7
25	Zhang Y	2019	China	ICCA	322	I–IV	57	60.25%	Surgery	44	OS/DFS	NLR ≥ 3
26	Wu YH	2019	China	ICCA	123	I–IV	57	54.47%	Surgery	29.1	OS	NLR ≥ 2.05
27	Sellers CM	2019	USA	ICCA	131	I–IV	65	51.90%	Surgery	13	OS	NLR ≥ 3.96
28	Lin J	2019	China	ICCA	218	I–IV	60	56.90%	Surgery	NR	OS	NLR ≥ 2.94
29	Hu HJ	2019	China	ECCA	134	I–IV	60	63.01%	Surgery	NR	OS	NLR ≥ 3
30	Hoshimoto S	2019	Japan	ECCA	53	I–IV	70	58.00%	Surgery	18	OS/DFS	NLR ≥ 1.97
31	Buettner S	2018	Netherlands	ICCA	991	I–IV	59	54.10%	Surgery	29	OS	NLR ≥ 5
32	Yoh T	2017	Japan	ICCA	141	I–IV	65	63.00%	Surgery	NR	OS	NLR ≥ 5
33	Omichi K	2017	USA	ICCA	119	I–IV	58	57.14%	Non-surgery	NR	OS/DFS	NLR ≥ 3
34	Nam K	2017	Korea	ICCA	377	I–IV	60	69.00%	Surgery	NR	OS	NLR ≥ 2.7
35	Kitano Y	2017	Japan	ECCA	120	I–IV	58	68.33%	Surgery	NR	OS/DFS	NLR ≥ 2.8
36	Cho H	2017	Korea	ICCA	305	III–IV	59	61.50%	Non-surgery	25	OS/DFS	NLR ≥ 2.8
37	Okuno M	2016	Japan	ECCA	219	III–IV	65	58.45%	Non-surgery	80.4	OS	NLR ≥ 5
38	Okuno M	2016	Japan	ECCA	534	I–IV	66	62.92%	Surgery	78	OS	NLR ≥ 3
39	Lin GH	2016	China	ICCA	102	I–IV	58	64.71%	Surgery	NR	OS/DFS	NLR ≥ 3
40	Lee BS	2016	Korea	CCA	221	III–IV	62	69.20%	Non-surgery	NR	OS/DFS	NLR ≥ 5
41	Ha H	2016	Korea	CCA	534	III–IV	60	65.20%	Non-surgery	95.3	OS	NLR ≥ 3.49
42	Beal EW	2016	USA	ECCA	525	I–IV	68	50.67%	Surgery	NR	OS/DFS	NLR ≥ 5
43	Chen Q	2016	China	ICCA	322	I–IV	58	60.25%	Surgery	NR	OS/DFS	NLR ≥ 2.49
44	Chen Q	2015	China	ICCA	322	I–IV	58	60.25%	Surgery	NR	OS/DFS	NR
45	McNamara MG	2014	Canada	CCA	864	I–IV	65	51.39%	Mix*	14.4	OS	NLR ≥ 3
46	Iwaku A	2014	USA	CCA	52	III–IV	70	59.62%	Non-surgery	4	OS	NLR ≥ 4
47	Dumitrascu T	2013	Romania	ECCA	90	I–IV	58	No	Surgery	68	OS/DFS	NLR ≥ 3.3
48	Gomez D	2008	UK	ICCA	27	I–IV	57	31.00%	Surgery	23	OS/DFS	NLR ≥ 5

Mix*, including 326 surgical and 538 non-surgery cases, CCA cholangiocarcinoma, DFS disease-free surviva, ECCA extrahepatic cholangiocarcinoma, ICCA intrahepatic cholangiocarcinoma, NLR neutrophile-to-lymphocyte ratio, NR not reported, OS overall survival, Ref reference.