Table 1. Main characteristics of the additional studies.
| Study | Year | Country | Age (mean or median) | No. (male/female) | Treatment | Histology | Intent | Stage | Cut-off value | HR | Study type |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Dutta et al. (4) | 2012 | UK | 75 | 112 (85/27) | S1 | SCC, ADC | Cur | I–IV | 150,300 | U | Uni/Re |
| Noble et al. (5) | 2013 | UK | 67 | 246 (195/51) | S1 | SCC, ADC | Cur | I–IV | 150 | U | Uni/Re |
| Yuan et al. (6) | 2014 | China | 63.1±9.7 | 327 (282/45) | S1 | ADC | Cur | I–IV | 150,300 | U | Uni/Re |
| Liu et al. (7) | 2015 | China | 59.2±7.9 | 326 (283/43) | S | SCC | Cur | I–IV | 166.5 | U/M | Uni/Re |
| Chen et al. (8) | 2016 | China | 59.1±7.9 | 323 (281/42) | S | SCC | Cur | I–III | 150 | U/M | Uni/Re |
| Wan et al. (9) | 2016 | China | 63.0 | 179 (150/29) | CRT | SCC, ADC | Cur | I–III | 180 | U | Uni/Re |
| Xie et al. (10) | 2016 | China | 58.1 | 317 (244/73) | S2 | SCC | Cur | I–III | 103 | U/M | Uni/Re |
S, surgery; S1, surgery ± neo chemo-radiotherapy; CRT, chemo-radiotherapy; S2, surgery ± adjuvant chemo-radiotherapy; SCC, squamous cell carcinoma; ADC, adenocarcinoma; Cur, curative intent; HR, hazard ratio; Uni, unicentric; Re, retrospective; U, univariate analysis; M, multivariate analysis.