Over the past decades, a large number of meta-analyses have been done to investigate the association between GSTM1 and GSTT1 polymorphisms and various cancers, including brain tumors [75], hepatocellular carcinoma [76], [77], colorectal cancer [78], [79], gastric cancer [80]–[84], breast cancer [85]–[90], bladder cancer [91]–[93], lung cancer [94]–[99], esophageal cancer [100], [101], prostate cancer [102], [103], nasopharyngeal carcinoma [104], head and neck cancer [105], oral and laryngeal cancer [106]–[108], and acute leukaemia [109], [110]. This evidence concerns the gene GSTM1 and colorectal cancer.