CA 19-9 as a marker in addition to CEA to monitor colorectal cancer. 
Carcinoembryonic antigen is the commonly used tumor marker in patients with colorectal cancer, and CA 19-9 might be an additional marker.  The aim of this retrospective study was to investigate whether CA 19-9 levels can be used to monitor the disease process in patients with colorectal cancer who had no elevated CEA levels.  The secondary aim was to determine if preoperative increased levels of CEA and CA 19-9 were associated with mortality.  Two sets of data from patients with histologically confirmed colorectal cancer, were included in a single-center study.  First, patients with a minimum of 3 serial measurements of CA 19-9 and CEA tumor markers were related to the clinical course of their disease.  Second, patients with preoperative levels of CEA and CA 19-9 were related to survival.  In patients with colorectal cancer and 3 serial measurements of tumor markers, 7.3% had only increased CA 19-9 levels without increased CEA levels, and 55.4% of the patients had an increase of CA 19-9 and CEA levels.  In the patients with available preoperative markers, patients with only an increase of CA 19-9 had a significantly decreased 5-year survival compared with patients with an increase of only CEA (P = .013).  CA 19-9 can be used as additional marker to follow the disease process in patients with colorectal cancer without an increase in CEA level.  Patients with preoperative increased CA 19-9 level had a poorer 5-year survival than patients with preoperative increased CEA levels.