Tumor Markers

Key Information

Prognostic (what treatment to use if the tumor should recur)

CEA (Carcinoembryonic Antigen)

A blood test measuring the presence of an antigen in malignancies arising in endodermal (embryonic) or gastrointestinal tissue. Persistent elevated levels indicate residual or recurrent metastatic carcinoma. CEA assay is nonspecific for identifying a primary site, but it does indicate the presence of malignancy. Smokers may have an elevated CEA without malignant disease.

Normal range:
< 2.5 ng/ml. Normal range may vary somewhat depending on the brand of assay used. Levels > 10 ng/ml suggest extensive disease and levels > 20 ng/ml suggest metastatic disease.

Other Tumor Markers

CA 19-9 (Cancer Antigen 19-9)

Monitors post-therapeutic gastrointestinal cancer for recurrence; nonspecific to colorectal cancer

CA 195 (Cancer Antigen 195)

Detects colon cancer; changing level indicates progression or regression of tumor load

Go to the Tumor Markers page of the Diagnostic Tests module for more information.