Table 1. Characteristics of studies included in the meta-analysis.
| First author | Year | Cancer type | Country | Ethnicity | Source of control groups | Cases/controls | P of HWE |
| Howell | 2001 | Melanoma | UK | European | HB | 165/158 | 0.69 |
| MartíNez-Escribano | 2002 | Melanoma | Spain | European | HB | 42/48 | 0.58 |
| Roh | 2002 | Cervical Cancer | Korea | Asian | HB | 144/179 | 0.72 |
| El–Omar | 2003 | Esophageal Cancer | USA | Mixed | PB | 161/210 | 0.43 |
| El–Omar | 2003 | Gastric Cancer | USA | Mixed | PB | 314/210 | 0.43 |
| Heneghan | 2003 | Hepatocellular Carcinoma | China | Asian | HB | 98/97 | 0.02 |
| Munro | 2003 | Hodgkin Lymphoma | UK | European | HB | 147/110 | 0.11 |
| Wu | 2003 | Gastric Cancer | Taiwan | Asian | HB | 220/230 | 0.23 |
| Basturk | 2004 | Renal Cell Cancer | Turkey | Mixed | HB | 29/50 | 0.32 |
| Maranda | 2004 | Diffuse Large B-Cell Lymphoma | France | European | HB | 199/112 | 0.54 |
| Savage | 2004 | Esophageal Cancer | China | Asian | PB | 119/386 | 0.38 |
| Savage | 2004 | Gastric Cancer | China | Asian | PB | 84/386 | 0.38 |
| Zhang | 2004 | Basal Cell Carcinoma | China | European | HB | 241/260 | 0.32 |
| Alonso | 2005 | Melanoma | Spain | European | HB | 98/100 | 0.21 |
| Alpízar-Alpízar | 2005 | Gastric Cancer | Costa Rica | Mixed | HB | 45/45 | 0.01 |
| Guzowski | 2005 | Breast Cancer | USA | Mixed | HB | 50/25 | 0.71 |
| Guzowski | 2005 | Leukemia | USA | Mixed | HB | 17/25 | 0.71 |
| Langsenlehner | 2005 | Breast Cancer | Australia | European | PB | 500/496 | 0.82 |
| Lee | 2005 | Gastric Cancer | Korea | Asian | HB | 122/120 | 0.06 |
| Macarthur | 2005 | Colorectal Cancer | Scotland | European | PB | 258/403 | 0.46 |
| Mazur | 2005 | Myeloma | Poland | European | HB | 54/50 | 0.22 |
| Shih | 2005 | Non-small Cell Lung Cancer | Taiwan | Asian | HB | 154/205 | 0.91 |
| Tseng | 2005 | Hepatocellular Carcinoma | Taiwan | Asian | HB | 208/184 | 0.57 |
| Zambon | 2005 | Gastric Cancer | Italy | European | HB | 129/644 | 0.70 |
| Zoodsma | 2005 | Cervical Cancer | Netherlands | European | PB | 654/606 | 0.21 |
| Braicu | 2006 | Ovarian Cancer | Germany | European | HB | 147/129 | 0.90 |
| Crivello | 2006 | Colorectal Cancer | Italy | European | HB | 62/124 | 0.72 |
| Kamangar | 2006 | Gastric Cancer | Filand | European | PB | 112/208 | 0.78 |
| Lan | 2006 | Non-Hodgkin’s Lymphoma | USA | European | PB | 482/563 | 0.03 |
| Pratesi | 2006 | Nasopharyngeal Carcinoma | Italy | European | PB | 89/130 | 0.27 |
| Purdue | 2006 | Non-Hodgkin’s Lymphoma | Australia | European | PB | 540/489 | 0.87 |
| Scola | 2006 | Breast Cancer | Italy | European | HB | 84/106 | 0.07 |
| Sicinschi | 2006 | Gastric Cancer | Mexico | European | HB | 181/369 | 0.38 |
| Sugimoto | 2006 | Gastric Cancer | Japan | Asian | HB | 105/168 | 0.42 |
| Cozar | 2007 | Colon Cancer | Spain | European | HB | 95/175 | 0.39 |
| Cozar | 2007 | Renal Cell Cancer | Spain | European | HB | 127/175 | 0.39 |
| Eder | 2007 | Prostate Cancer | Australia | European | PB | 547/545 | 0.44 |
| Garcia-Gonzalez | 2007 | Gastric Cancer | Spain | European | HB | 404/404 | 0.08 |
| Gonullu | 2007 | Breast Cancer | Turkey | Mixed | HB | 38/24 | 0.59 |
| Ivansson | 2007 | Cervical Cancer | Sweden | European | HB | 1282/288 | 0.33 |
| Purdue | 2007 | Testicular Germ Cell Tumors | USA | European | PB | 505/604 | 0.28 |
| Vogel | 2007 | Basal Cell Carcinoma | Denmark | European | PB | 304/315 | 0.92 |
| Wei | 2007 | Nasopharyngeal Carcinoma | China | Asian | HB | 198/210 | 0.84 |
| Cacev | 2008 | Colon Cancer | Croatia | European | PB | 160/160 | 0.40 |
| Colakogullari | 2008 | Lung Cancer | Turkey | Mixed | HB | 44/59 | 0.74 |
| Crusius | 2008 | Gastric Cancer | Netherlands | European | PB | 237/1122 | 0.05 |
| Erdogan | 2008 | Thyroid Cancer | Turkey | Mixed | HB | 42/113 | 0.81 |
| Faupel-Badger | 2008 | Prostate Cancer | Filand | European | PB | 511/386 | 0.54 |
| Kube | 2008 | Non-Hodgkin’s Lymphoma | Germany | European | HB | 500/236 | 0.35 |
| Vogel | 2008 | Lung Cancer | Denmark | European | PB | 403/744 | 0.34 |
| Yao | 2008 | Oral Cancer | China | Asian | HB | 280/300 | 0.81 |
| Zabaleta | 2008 | Prostate Cancer | USA | African | HB | 67/128 | 0.19 |
| Zabaleta | 2008 | Prostate Cancer | USA | European | HB | 479/401 | 0.44 |
| Ando | 2009 | Gastric Cancer | Japan | Asian | HB | 330/190 | 0.06 |
| Kang | 2009 | Gastric Cancer | Korea | Asian | HB | 333/332 | 0.59 |
| Schoof | 2009 | Melanoma | Germany | European | HB | 164/162 | 1.00 |
| Tsilidis | 2009 | Colorectal Cancer | USA | Mixed | PB | 203/361 | 0.58 |
| Wang | 2009 | Prostate Cancer | USA | Mixed | PB | 255/255 | 0.64 |
| Hart | 2010 | Non-small Cell Lung Cancer | Norway | European | PB | 434/433 | 0.01 |
| Kong | 2010 | Breast Cancer | China | Asian | HB | 315/322 | 0.01 |
| Liu | 2010 | Prostate Cancer | China | Asian | HB | 262/270 | 0.48 |
| Vancleave | 2010 | Prostate Cancer | USA | African | HB | 189/651 | 0.06 |
| Li | 2011 | Hepatocellular Carcinoma | China | Asian | PB | 150/347 | − |
| Liu | 2011 | Gastric Cancer | China | Asian | HB | 234/243 | 0.77 |
| Shekari | 2011 | Cervical Cancer | India | European | HB | 200/200 | 0.05 |
| Zeng | 2011 | Gastric Cancer | China | Asian | HB | 151/153 | 0.15 |
| Andersen | 2012 | Colorectal Cancer | Denmark | European | PB | 378/775 | 0.33 |
| He | 2012 | Gastric Cancer | China | Asian | HB | 196/248 | 0.10 |
| Pooja | 2012 | Breast Cancer | India | European | HB | 200/200 | 0.08 |
| Zhang | 2012 | Non-Hodgkin’s Lymphoma | China | Asian | PB | 514/557 | 0.87 |
HB, hospital based; HWE: Hardy–Weinberg Equilibrium; PB, population based.