CEACAM5 and colorectal cancer: Based on this background, we conducted a randomized clinical trial (the COLOFOL trial) that included 2509 patients with stage II or III colorectal cancer.7 The patients were randomly allocated to either follow-up testing with computed tomography (CT) scan of the thorax and abdomen and serum carcinoembryonic antigen (CEA) screening at 6, 12, 24, and 36 months (1253 patients), or at 12 or 36 months after surgery (1256 patients).