In several subgroups, including the subgroups defined by male sex, age ≥70 years, AJCC stage IV, adenocarcinoma pathology, low histological grades, lack of a mucinous component, presence of lymphovascular or perineural invasion, and CEA ≥ 6 mg/dL or CA199 ≥ 40 mg/dL, patients with left-sided colon cancer had better progression-free survival than the equivalent middle/low rectal tumour subgroups (Fig. 3). This evidence concerns the gene CEACAM5 and rectal neoplasm.