Table 1. Main characteristics of included studies.
| First author | Year | Country | Ethnicity | Specimens | Cancer type | Method | Cut-off* | Follow-up (month) | Number | Analysis | Survival |
| Yang [19] | 2011 | China | Asian | Tissue | HCC | RT-qPCR | NR | 18.6 (median) | 60 | Multivariable | RFS |
| Kogo [20] | 2011 | Japan | Asian | Tissue | CRC | RT-qPCR | 0.027 | 36 (mean) | 100 | Multivariable | OS |
| Lu [40] | 2012 | Italy | Caucasian | Tissue | BC | RT-qPCR | NR | 86 (median) | 336 | Multivariable | OS, RFS |
| Li [41] | 2012 | China | Asian | Tissue | LSCC | RT-qPCR | NR | 60 (total) | 72 | Multivariable | OS |
| Nie [42] | 2013 | China | Asian | Tissue | NPC | ISH | 6 | 69 (median) | 160 | Multivariable | OS |
| Nakagawa [43] | 2013 | Japan | Asian | Tissue | NSCLC | RT-qPCR | 2 | 31.4 (median) | 77 | Univariable | DFS |
| Lv [44] | 2013 | China | Asian | Tissue | ESCC | ISH | 6 | 60 (total) | 93 | Univariable | OS |
| Li [45] | 2013 | China | Asian | Tissue | ESCC | RT-qPCR | 125 | 60 (total) | 100 | Multivariable | OS |
| Ge [46] | 2013 | China | Asian | Tissue | ESCC | RT-qPCR | NR | 60 (total) | 137 | Multivariable | OS, MFS |
| Liu [47] | 2013 | China | Asian | Tissue | NSCLC | RT-qPCR | 8.57 | 60 (total) | 42 | Univariable | OS |
| Chen [48] | 2013 | China | Asian | Tissue | ESCC | RT-qPCR | 26.6 | 38 (mean) | 78 | Multivariable | OS |
| Zhang [49] | 2013 | China | Asian | Tissue | GBM | GSEA | NR | 50 (totoal) | 89 | Multivariable | OS |
| Sørensen [50] | 2013 | Denmark | Caucasian | Tissue | BC | Microarray | 0.6 | 217.2 (mean) | 164 | Multivariable | MFS |
| Svoboda [51] | 2014 | Czech | Caucasian | Tissue, Blood | CRC | RT-qPCR | 0.7, 4.4 | 35 (mean) | 73, 84 | Multivariable | OS |
| Qiu [52] | 2014 | China | Asian | Tissue | EOC | RT-qPCR | NR | 50.5 (median) | 64 | Univariable | OS, DFS |
| Huang [53] | 2014 | China | Asian | Tissue | Cervical | RT-qPCR | NR | 42 (mean) | 218 | Multivariable | OS |
| Liu [54] | 2014 | China | Asian | Tissue | GC | RT-qPCR | NR | 50 (totoal) | 78 | Univariable | OS |
| Wu [55] | 2014 | China | Asian | Tissue | CRC | RT-qPCR | 5 | 55.5 (median) | 120 | Multivariable | OS, MFS |
| Yan [29] | 2014 | China | Asian | Tissue | Bladder | RT-qPCR | NR | 60 (total) | 110 | Multivariable | RFS |
*cancerous/noncancerous
HCC, hepatocellular carcinoma; CRC, colorectal cancer; BC, breast cancer; LSCC, laryngeal squamous cell carcinoma; NPC, nasopharyngeal carcinoma; NSCLC, non-small cell lung cancer; ESCC, esophageal squamous cell carcinoma; GBM, glioblastoma multiforme; EOC, epithelial ovarian cancer; GC, gastric cancer; RT-qPCR, real-time quantitative PCR; ISH, in situ hybridization; GSEA, gene set enrichment analysis; NR, not reported; OS, overall survival; MFS, metastasis-free survival; RFS, recurrence-free survival; DFS, disease-free survival.