APR: Abdominoperineal resection; LAR: Low anterior resection; mtLNR: Metastatic lymph node ratio, OS: Overall survival; DFS: Disease-free survival; TNM: Tumor, node, metastasis; LVI: Lymphovascular invasion; PNI: Perineural invasion; CEA: Carcinoembryonic antigen; CA19-9: Carbohydrate antigen 19-9. The gene discussed is CEACAM5; the disease is neoplasm.