CEACAM5 and rectal cancer: No statistically significant difference was observed between the two CRT sequence groups in pre-treatment characteristics, including age, gender, histological grade, serum carcinoembryonic antigen level and clinical stage, except for tumor location; even after excluding upper rectal cancer, significantly more patients with low rectal cancer were treated initially with pre-operative CRT rather than up-front surgery (36.9% vs. 23.9%; P = 0.001).