Table 1. Characteristics of the studies included in the meta-analysis.
| Study | Year | Ethnicity | Cancertype | Controlsource | No. ofcases/controls | Mean age ofcases/controls | Gender distributionin cases/controls(male %) | Genotypingmethod | PHWE forcontrols |
| Ma [15] | 1999 | American | CRC | PB | 356/476 | NA/NA | 100/100 | RFLP | 0.15 |
| Le Marchand [21] | 2002 | American | CRC | PB | 539/652 | 66.0/67.0 | 60.8/57.9 | RFLP | 0.54 |
| Matsuo [22] | 2002 | Japanese | CRC | HB | 142/241 | NA/NA | 58.9/49.0 | RFLP | 0.28 |
| Pufulete [23] | 2003 | British | CRC | HB | 28/76 | 68.9/58.0 | 46.0/45.0 | RFLP | 0.07 |
| Ulvik [24] | 2004 | Norwegian | CRC | PB | 2168/2192 | NA/NA | 63.5/63.5 | Taqman | 0.34 |
| Matsuo [25] | 2005 | Japanese | CRC | HB | 257/771 | 58.8/59.0 | 63.0/63.0 | RFLP | 0.4 |
| Ulrich [26] | 2005 | American | CRC | PB | 1600/1962 | 64.9/65.0 | 56.0/53.0 | Taqman | 0.13 |
| Yang [27] | 2005 | Japanese | EC | HB | 165/494 | 61.4/61.4 | 89.7/89.7 | RFLP | 0.43 |
| Wang [28] | 2006 | Chinese | PC | HB | 101/337 | NA/NA | 64.4/65.6 | RFLP | 0.86 |
| Koushik [29] | 2006 | American | CRC | PB | 363/804 | 68.2/68.0 | 47.6/42.0 | Taqman | 0.18 |
| Chen [30] | 2006 | Chinese | CRC | PB | 199/413 | 62.5/61.9 | 50.8/51.7 | RFLP | 0.18 |
| Curtin [31] | 2007 | American | CRC | PB | 916/1974 | NA/NA | NA/NA | Taqman | 0.09 |
| Zhang [32] | 2007 | Polish | GC | PB | 293/413 | 63.0/63.7 | 66.2/64.6 | Taqman | 0.22 |
| Theodoratou [33] | 2008 | Scottish | CRC | PB | 999/1010 | 62.3/62.7 | 57.3/56.9 | Array | 0.27 |
| Guerreiro [34] | 2008 | Portuguese | CRC | PB | 196/200 | 64.2/62.2 | 53.1/53.0 | Taqman | 0.41 |
| Suzuki [35] | 2008 | Japanese | PC | HB | 157/783 | NA/NA | 71.3/71.3 | Taqman | 0.56 |
| Zhang [36] | 2008 | Chinese | CRC | HB | 298/300 | 57.7/57.6 | 56.3/56.7 | RFLP | 0.13 |
| Ott [37] | 2008 | German | EC, GC | HB | 588/245 | 59.7/39 | 70.0/76.7 | RFLP | 0.97 |
| Steck [38] | 2008 | American | CRC | PB | 546/855 | 63.8/65.9 | NA/NA | Taqman | 0.14 |
| de Vogel [39] | 2009 | Dutch | CRC | PB | 696/1805 | NA/NA | 55.0/50.2 | SNaPShot | 0.31 |
| Zhang [40] | 2009 | Chinese | CRC | HB | 476/835 | 54.3/52.0 | 57.1/55.1 | RFLP | 0.67 |
| Eussen [41] | 2010 | European | CRC | PB | 1329/2364 | 58.9/58.7 | 51.0/53.0 | Mass spectrometry | 0.52 |
| Levine [42] | 2010 | American | CRC | PB | 1806/2879 | 53.5/54.0 | 51.3/44.4 | iPLEX | 0.17 |
| Eussen [43] | 2010 | European | GC | PB | 243/616 | 58.9/58.7 | 41.0/41.0 | Mass spectrometry | 0.12 |
| Jokić [44] | 2011 | Croatian | CRC | PB | 300/300 | 62.2/61.4 | 54.0/50.6 | Taqman | 0.82 |
| Guimarães [45] | 2011 | Brazilian | CRC | PB | 113/188 | 59.0/54.0 | 53.1/64.4 | RFLP | 0.06 |
| Kim [46] | 2011 | Korean | CRC | HB | 67/53 | 61.8/58.7 | 52.2/43.4 | RFLP | 0.12 |
| Cui [47] | 2012 | Chinese | HCC | PB | 356/641 | 56.6/58.7 | 83.1/43.5 | RFLP | 0.92 |
| Martinelli [48] | 2012 | Italian | CRC | PB | 71/80 | 69.0/58.0 | 59.2/53.8 | RFLP | 0.21 |
NA: not available, HB: hospital-based, PB: population-based, CRC: colorectal cancer, EC: esophagus cancer, HCC: hepatocellular carcinoma, GC: gastric cancer, PC: pancreatic cancer.