CTLA4 and colorectal cancer: For CTLA-4 60G/A (rs3087243) polymorphism, there were 17 articles [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34] met the inclusion criteria with 5571 cases and 5567 controls, 1 article (Cozar et al.)[20] provided 2 kinds of cancers (renal cancer and colorectal cancer) in CTLA-4 60G/A polymorphism, thus, each type of cancer in these articles was treated as a separated case-control study.