Furthermore, we also found that the 5-FU-based CRT group or OXA-based CRT group combined with the XPF–ERCC1 blocker could reduce the XPF level and increase the expression of γ-H2AX in colorectal cancer cells suggesting that the XPF–ERCC1 blocker could increase the cytotoxicity of radiation and chemotherapy drugs by inhibiting the XPF–ERCC1-based DNA repair. Here, ERCC4 is linked to colorectal cancer.