Table 1. Characteristics of all included studies.
| Study | Year | Country | Ethnicity | Follow-up (month) | Sample size | Gender (M/F) | TNM stage | Cut-off | Treatment methods | Outcome | Hazard ratio | Study design | NOS score |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Liu15 | 2013 | China | Asian | To Aug 2012 | 210 | 139/71 | III–IV | 152.6 | Chemotherapy | OS | R | Retrospective | 8 |
| Unal19 | 2013 | Turkey | Caucasian | NA | 94 | 88/6 | II–IIIB | 194 | Chemoradiotherapy | OS,DFS | R | Retrospective | 8 |
| Pinato17 | 2014 | UK | Caucasian | To Sep 2012 | 220 | 110/110 | I–III | 300 | Surgery | OS | R | Prospective | 7 |
| Zhang20 | 2014 | China | Asian | 46(1–78) | 400 | 272/128 | I–II | 171 | Surgery | OS,DFS | R | Retrospective | 8 |
| Cannon16 | 2015 | USA | Caucasian | 17(median) | 59 | 31/28 | I | 146 | Radiotherapy | OS | E | Retrospective | 7 |
| Kawashima21 | 2015 | Japan | Asian | NA | 1043 | 671/372 | I–III | 300 | Surgery | OS | R | Retrospective | 7 |
| Kos22 | 2015 | Turkey | Caucasian | 33(1–128) | 145 | 130/15 | I–IV | 198.2 | Mixed | OS | R | Retrospective | 9 |
| Miyazaki25 | 2015 | Japan | Asian | NA | 97 | 62/35 | I | 118 | Surgery | OS,DFS | E | Retrospective | 8 |
| Shaverdian23 | 2015 | USA | Caucasian | 28.9(median) | 118 | NA | I–II | 187.27 | Radiotherapy | OS | E | Retrospective | 7 |
| Wu18 | 2015 | China | Asian | To Dec 2013 | 366 | 246/120 | III–IV | 119.5 | Chemotherapy | OS,PFS | R | Retrospective | 7 |
| Zhang24 | 2015 | China | Asian | 43.5(1–99) | 678 | 449/229 | I–III | 106 | Surgery | OS,DFS | R | Retrospective | 7 |
NA: not available; R: reported in text; E: estimated; OS: overall survival; DFS: disease free survival; PFS: progressi on free survival; NOS: Newcastle–Ottawa Quality Assessment Scale.