This study investigated the relationship between changes in the levels of carcinoembryonic antigen (CEA) and colorectal cancer response to treatment. Researchers suggested that CEA levels are associated with tumor response and can be used as a prognostic factor.

In 2014 the European Society for Medical Oncology recommended the use of CEA (a protein found elevated in certain types of cancer) in the blood as a tumor predictive factor for colorectal cancer. CT scans are the standard method for following-up tumor progression. However, it exposes patients to radiation and has a much higher cost than a CEA blood test.

There are no studies that investigate the changes in CEA levels after the first line of chemotherapy in advanced colorectal cancer. Therefore, it is unknown if changes in CEA levels predict tumor response and disease progression.

This study included information about 114 patients with advanced colorectal cancer. CEA blood levels were measured at the beginning of the study and throughout the treatment until disease growth or spread. They were divided into 5 different groups according to their CEA change pattern. Patients from group A had a first fast CEA decrease which turned into a slow increase. Patients from group B had a first slow CEA decrease that turned into a slow increase. Group C had a continually slow CEA increase. Group D had a continually fast CEA increase and group E had an initial fast CEA decrease that turned into a fast increase.

Patients from group A had the longest overall survival (37.9 months) and progression-free survival (time from treatment to tumor growth or spread; 13.7 months). Group E had the shortest overall survival (15.3 months). An increase in CEA level by 2.7% or more between week 12 and 18 was associated with a poorer overall survival.

The authors concluded that changes in CEA levels are associated to tumor response to treatment. The authors suggest that CEA can replace a CT scan in the follow-up of patients with advanced colorectal cancer.

This study had a limited number of participants. Larger studies are needed for more conclusive evidence.

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