Table 1. The characteristics of included studies for TNF-α polymorphisms and CRC.
| First author, year | Country | Ethnicity | Source of controls | Sample size | Genotype distribution | P-value for HWE | NOS score | |
|---|---|---|---|---|---|---|---|---|
| Cases | Controls | |||||||
| -238 G/A | GG/GA/AA | |||||||
| Garrity-Park 2008 [13] | USA | Mixed | HB | 114/114 | 109/5/0 | 107/6/1 | 0.017 | 8 |
| Gutiérrez-Hurtado 2016 [15] | Mexico | Mixed | PB | 143/49 | 127/14/2 | 42/6/1 | 0.199 | 7 |
| Hamadien 2016 [16] | Saudi Arabia | Caucasian | PB | 100/100 | 86/13/1 | 97/2/1 | <0.001 | 8 |
| Jang 2001 [17] | Korea | Asian | PB | 27/92 | 27/0/0 | 80/11/1 | 0.391 | 8 |
| Kapitanović 2014 [18] | Croatia | Caucasian | PB | 200/200 | 181/18/1 | 188/11/1 | 0.076 | 8 |
| Madani 2008 [24] | Iran | Caucasian | PB | 51/46 | 51/0/0 | 45/1/0 | 0.941 | 7 |
| Wang 2008 [31] | China | Asian | PB | 343/670 | 320/22/1 | 620/50/0 | 0.316 | 8 |
| -308 G/A | GG/GA/AA | |||||||
| Banday 2016 [10] | India | Caucasian | PB | 142/184 | 124/18/0 | 150/34/0 | 0.167 | 8 |
| Basavaraju 2015 [11] | UK | Caucasian | PB | 388/495 | 253/117/18 | 309/167/19 | 0.543 | 7 |
| Burada 2013 [12] | Romania | Caucasian | PB | 144/233 | 115/26/3 | 189/42/2 | 0.842 | 8 |
| Garrity-Park 2008 [13] | USA | Mixed | HB | 114/114 | 52/49/13 | 92/20/2 | 0.464 | 8 |
| Gunter 2006 [14] | USA | Mixed | PB | 217/202 | 146/59/12 | 139/57/6 | 0.957 | 8 |
| Gutiérrez-Hurtado 2016 [15] | Mexico | Mixed | PB | 164/209 | 139/21/4 | 180/27/2 | 0.392 | 7 |
| Hamadien 2016 [16] | Saudi Arabia | Caucasian | PB | 100/100 | 67/23/10 | 59/23/18 | <0.001 | 8 |
| Jang 2001 [17] | Korea | Asian | PB | 27/92 | 24/3/0 | 85/7/0 | 0.704 | 8 |
| Kapitanović 2014 [18] | Croatia | Caucasian | PB | 200/200 | 163/35/2 | 163/35/2 | 0.937 | 8 |
| Landi 2003 [19] | France | Caucasian | PB | 363/320 | 278/80/5 | 234/76/10 | 0.220 | 7 |
| Li 2011 [21] | China | Asian | PB | 180/180 | 156/15/9 | 160/19/1 | 0.599 | 8 |
| Li 2017 [22] | China | Asian | PB | 569/570 | 500/66/3 | 493/75/2 | 0.632 | 8 |
| Macarthur 2005 [23] | UK | Caucasian | PB | 246/389 | 157/74/15 | 224/145/20 | 0.577 | 8 |
| Park 1998 [25] | Korea | Asian | PB | 136/331 | 40/71/25 | 148/151/32 | 0.465 | 7 |
| Stanilov 2014 [26] | Bulgaria | Caucasian | PB | 119/177 | 88/28/3 | 135/40/2 | 0.612 | 8 |
| Suchy 2008 [27] | Poland | Caucasian | PB | 350/350 | 254/87/9 | 248/95/7 | 0.546 | 8 |
| Theodoropoulos 2006 [28] | Greece | Caucasian | PB | 222/200 | 152/56/14 | 146/44/10 | 0.010 | 7 |
| Toth 2007 [29] | Hungary | Caucasian | PB | 183/141 | 132/48/3 | 111/30/0 | 0.157 | 7 |
| Tsilidis 2009 [30] | USA | Mixed | PB | 204/372 | 146/55/3 | 275/90/7 | 0.908 | 7 |
| Wang 2008 [31] | China | Asian | PB | 344/669 | 284/58/2 | 554/111/4 | 0.538 | 8 |
| -857 C/T | CC/CT/TT | |||||||
| Garrity-Park 2008 [13] | USA | Mixed | HB | 114/114 | 98/16/0 | 92/22/0 | 0.254 | 8 |
| Hamadien 2016 [16] | Saudi Arabia | Caucasian | PB | 100/100 | 85/15/0 | 85/15/0 | 0.417 | 8 |
| Kapitanović 2014 [18] | Croatia | Caucasian | PB | 200/200 | 130/64/6 | 126/67/7 | 0.599 | 8 |
| Landi 2006 [20] | Spain | Caucasian | PB | 281/268 | 219/58/4 | 220/45/3 | 0.684 | 7 |
| Suchy 2008 [27] | Poland | Caucasian | PB | 350/350 | 253/88/9 | 242/98/10 | 0.983 | 8 |
| -863 C/A | CC/CA/AA | |||||||
| Garrity-Park 2008 [13] | USA | Mixed | HB | 114/114 | 84/28/2 | 80/33/1 | 0.224 | 8 |
| Suchy 2008 [27] | Poland | Caucasian | PB | 350/350 | 262/77/11 | 257/83/10 | 0.302 | 8 |
| -1031 T/C | TT/TC/CC | |||||||
| Garrity-Park 2008 [13] | USA | Mixed | HB | 114/114 | 79/31/4 | 75/36/3 | 0.588 | 8 |
| Kapitanović 2014 [18] | Croatia | Caucasian | PB | 200/200 | 132/56/12 | 135/54/11 | 0.082 | 8 |
| Suchy 2008 [27] | Poland | Caucasian | PB | 350/350 | 250/90/10 | 227/107/16 | 0.460 | 8 |
Abbreviations: CRC, colorectal cancer; HWE, Hardy–Weinberg equilibrium; NA, not available; NOS, Newcastle–Ottawa scale; TNF-α, tumor necrosis factor-α.