NAT2 and colorectal adenoma: The overall data from the seven studies containing 3,197 cases and 4,681 controls revealed no significant associations between NAT2 polymorphisms and colorectal adenoma risk (OR, 1.04; 95% CI, 0.90–1.21; P=0.043 for heterogeneity), suggesting that NAT2 polymorphisms may have little association with colorectal adenoma risk (Fig. 2).