Table 2.

Qualities of cohort studies are evaluated by modified Newcastle–Ottawa scale.

Ref	Author	Selection	Comparability	Outcomes	Quality score
17	Zhao JP	★★★★	★★	★★	9
18	Ma B	★★★	★★	★★	8
19	Zhang ZY	★★★★	★★	★★	9
20	Tsilimigras DI	★★★★	★★	★★	9
21	Ohira M	★★★★	★★	★★	9
22	Ji F	★★★★	★★	★★	9
23	Huh G	★★★★	★★	★★	9
24	Filippi L	★★★★	★★	★★	9
25	Zhang Y	★★★★	★★	★★	9
26	Wu YH	★★★	★★	★★	8
27	Sellers CM	★★★★	★★	★★	9
28	Lin J	★★★★	★★	★★	9
29	Hu HJ	★★★	★★	★★	8
30	Hoshimoto S	★★★	★★	★★	8
31	Buettner S	★★★★	★★	★	8
32	Yoh T	★★★	★★	★	6
33	Omichi K	★★★★	★★	★★	9
34	Nam K	★★★★	★★	★	8
35	Kitano Y	★★★★	★★	★★	9
36	Cho H	★★★★	★★	★	8
37	Okuno M	★★★★	★★	★★	9
38	Okuno M	★★★★	★★	★★	9
39	Lin GH	★★★★	★★	★	8
40	Lee BS	★★★★	★★	★★	9
41	Ha H	★★★★	★★	★★	9
42	Beal EW	★★★★	★★	★★	9
43	Chen Q	★★★★	★★	★★	9
44	Chen Q	★★★★	★★	★	8
45	McNamara MG	★★★★	★★	★★	9
46	Iwaku A	★★★★	★★	★★	9
47	Dumitrascu T	★★★★	★★	★	8
48	Gomez D	★★★★	★★	★	8

The quality of the included studies was assessed under six items of Hayden et al. All included translational studies reporting oncological outcome were evaluated in accordance with the Newcastle–Ottawa scale. The maximum score of the scale is nine points with studies being categorized as low (0–3 points), moderate (4–6 points) and high quality (7–9 points), respectively.