Preoperative serum CA19-9 should be routinely measured in the colorectal patients with preoperative normal serum CEA: A multicenter retrospective cohort study

Whether preoperative serum carbohydrate antigen 19–9 (CA19-9) is an independent prognostic factor and there are interactions of serum CA19-9 with carcinoembryonic antigen (CEA) on the risk of recurrence in colorectal cancer (CRC) patients are still not clarified.