Cumulative epidemiological evidence of an association was graded as strong for rs7903146 [odds ratio (OR) = 1.05, p = 4.13 × 10<sup>-5</sup> ] and rs7904519 (OR = 1.07, p = 2.02 × 10<sup>-14</sup> ) in breast cancer, rs11196172 (OR = 1.11, p = 2.22 × 10<sup>-16</sup> ), rs12241008 (OR = 1.13, p = 1.36 × 10<sup>-10</sup> ) and rs10506868 (OR = 1.10, p = 3.98 × 10<sup>-9</sup> ) in colorectal cancer, rs7086803 in lung cancer (OR = 1.30, p = 3.54 × 10<sup>-18</sup> ) and rs11196067 (OR = 1.18, p = 3.59 × 10<sup>-13</sup> ) in glioma, moderate for rs12255372 (OR = 1.12, p = 2.52 × 10<sup>-4</sup> ) in breast cancer and weak for rs7903146 (OR = 1.11, p = 0.007) in colorectal cancer.
The results indicated that the TCF7L2 rs11196172 polymorphism increases the risk of CRC independently, with no evidence of an interaction with diabetes or obesity.