ERCC4 and colorectal carcinoma: We used the Mann–Whitney U test to study the differences between the XPF groups (Table 4) and stratified the CRC patients based on age, gender, smoking, alcohol consumption, location, TNM stage, invasive extent, lymph node metastasis, distant metastasis, perineural invasion, vessel carcinoma embolus, growth pattern, differentiation degree and family history.