TCF7L2 and colorectal cancer: To date, many studies have been published investigating the association between TCF7L2 rs7903146 or rs12255372 (it is in high linkage disequilibrium with rs7903146) and several types of cancer, including breast cancer [4]–[8], prostate cancer [5], [9]–[12], colorectal cancer [5], [13]–[15], colon cancer [5], [16], lung cancer [5] and ovarian cancer [6].