| Lener M. et al. 2013 [20] | case-control | no data available on cases recruitment; controls were selected from Polish and Estonian registers | 338(169 colorectal cancer patients; 169 controls) | 6 |
| Connelly-Frost A. et al. 2009 [6] | case-control | cases from North Carolina cancer registry; population-based control (selected from 33-county area in central North Carolina) | 1691(643 cases; 1048 controls) | 5 |
| Fernández-Bañares F. et al. 2002 [8] | case-control | hospital-based cases; controls belonging to a big survey performed in Spain were included in the study | 87(52 cases; 35 controls) | 6 |
| Hughes D.J. et al. 2015 [14] | nested case-control | cases were identified during EPIC follow-up with a use of population cancer registries (Denmark, Italy, Netherlands, Spain, United Kingdom) and other methods: health insurance records, pathology registries, active contact of study subjects; controls were matched 1:1 by a study center, but no other data were available on the control’s recruitment | 1932(966 cases; 966 controls) | 7 |
| Peters U. et al. 2006 [27] | nested case-control | cases and controls were randomly selected from 42 037 participants in the screening group of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial | 1525(772 cases; 777 controls) | 6 |
| Wallace K. et al. 2003 [36] | nested case-control | cases and controls were recruited (including special criteria) from participants of the placebo-controlled trial (those have been chosen at six clinical centers in the U.S.) | 552(276 cases; 276 controls) | 5 |
| Takata Y. et al. 2011 [31] | nested case-control | cases were recruited mostly with a use of mass mailing which were age-targeted and media announcements in areas surrounding the 40 WHI clinical centers across the U.S.; controls were selected from all eligible women in the WHI study who were alive and had not been diagnosed with CRC at the time of the case’s diagnosis; | 1609(804 cases; 805 controls) | 5 |
| Ghadirian P. et al. 2000 [10] | case-control | mainly hospital-based cases, identified through the admission offices of 5 major teaching hospitals; population-based controls (modified random-digit dialing method) | 1736(1048 cases, 688 controls) | 4 |
| Kune G., Watson L. 2006 [18] | case-control | cases from the etiological arm of population-based investigation; controls were randomly chosen from community, Melbourne, Australia | 1442(715 cases; 727 controls) | 5 |
| Yang B. et al. 2014 [39] | cohort | participants from Cancer Prevention Study II Nutrition Cohort. II Nutrition Cohort was selected as a subgroup of larger CPS cohort in which approximately 1.2 million of people were enrolled by volunteers in all 50 states, the District of Columbia and Puerto Rico | 2284 | 6 |
| Williams C.D. et al. 2010 [38] | nested case-control | cases were chosen from the North Carolina Central Cancer Registry; controls <65 years were selected by using lists provided by the North Carolina Division of Motor Vehicles and the Center for Medicaid and Medicare Services for those 65 and older; controls were selected from subjects (African American or White) resided in one of 33 counties in central and eastern North Carolina. A randomized recruitment procedure was used for identifying cases and controls | 2076(1057 cases; 1019 controls) | 4 |
| Hansen R.D. et al. 2013 [12] | cohort | population-based cohort, which based on 54 208 members of the Diet, Cancer and Health Cohort Study | 54 208 | 5 |
