For patients with pCR or TRG 0 (23.2%; n = 13/56), 69.2% (n = 9) were female (p = 0.07), moderately differentiated adenocarcinomas (p = 0.09), CEA ≤ 3.0 (p = 0.11) and clinical T3 (p = 0.06); 61.5% (n = 8) of patients with pCR carried medium rectum tumors (p = 0.57) and underwent neoadjuvant treatment with 5-FU (p = 0.99). The gene discussed is CEACAM5; the disease is digestive system neoplasm.