Table 1. Characteristics of all eligible studies.
| Study | Year | Country | No. (male/female) | Age (mean or median) | Treatment | Intent | Stage | Cutoff value | Median OS (m) (low/high PLR) | HR (M/U) | Result | Histology | Study type |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feng et al. | 2013 | China | 43 (30/13) | 58.7±7.8 | Mix | Cur | I–III | 150 | NR | M | Positive | Small cell | Uni/Re |
| Feng et al. | 2014 | China | 483 (411/72) | 59.1±8.0 | S | Cur | I–III | 150 | NR | M/U | Positive | SCC | Uni/Re |
| Han et al. | 2015 | China | 218 (177/41) | 60.5 | Mix | Cur | I–III | 244 | 40/29.9 | M/U | Negative | SCC | Uni/Re |
| Xu et al. | 2015 | China | 468 (416/52) | 58 | Mix | Cur | I–III | 147 | NR | U | Negative | SCC | Uni/Re |
| He et al. | 2015 | China | 820 (526/294) | 60.0±9.3 | S or NR | NR | I–IV | 194 | NR | M | Negative | SCC + others | Uni/Re |
| Messager et al. | 2015 | UK | 153 (128/25) | 64.9 | Mix | Cur | I–III | 192 | NR | M/U | Positive | ADC | Uni/Re |
| Geng et al. | 2016 | China | 916 (696/220) | 60 | S | Cur | I–III | 120 | 53/36 | M/U | Negative | SCC | Uni/Re |
| Ji et al. | 2016 | China | 41 (38/3) | 56.6±7.2 | Mix | Cur | I–III | 130 | NR | U | Positive | SCC | Uni/Re |
| Sun et al. | 2016 | China | 362 (268/94) | 58 | Mix | Cur | I–III | 150 | NR | U | Negative | SCC | Uni/Re |
| Toyokawa et al. | 2016 | Japan | 185 (152/33) | 64 | Mix | Cur | I–IV | 193 | NR | M | Negative | SCC | Uni/Re |
| Zhang et al. | 2016 | China | 468 (376/92) | 59.5±9 | Mix | Cur | I–III | 117.07 | NR | M/U | Negative | SCC | Uni/Re |
| He et al. | 2017 | China | 317 (268/49) | 60 | Mix | Cur | I–IV | 150 | 44/22.1 | M | Positive | SCC | Uni/Re |
| Hirahara et al. | 2017 | Japan | 147 (132/15) | NR | S | Cur | I–III | 147 | NR | U | Negative | SCC | Uni/Re |
No., patient number; M, hazard ratio from multivariate analysis; U, HR from univariate analysis; Mix, mixed treatment, combing different treatment methods (such as surgery, radiotherapy, chemoradiotherapy or chemotherapy); S, surgery; NR, not reported; HR, hazard ratio; Intent, treatment intent; Cur, curative intent; OS, overall survival; SCC, squamous cell carcinoma; ADC, adenocarcinoma; Uni, Uni-centric; Re, retrospective.