Medical Health Encyclopedia

Researchers are continually seeking to identify tumor markers, substances (usually found in blood samples) that will assist in the diagnosis of cancer and in monitoring effects of treatment.

Carcinoembryonic Antigen (CEA). High blood levels of a protein called carcinoembryonic antigen (CEA) sometimes indicate the presence of colon cancer. Unfortunately, it is also elevated in other cancers and in some noncancerous conditions. CEA is not effective as a screening tool for healthy people, but might eventually be helpful for cancer patients.

• An advanced diagnostic technique called polymerase chain reaction (PCR) can detect genetic evidence of CEA. One study indicated that when these microscopic footprints of colon cancer are detected in the lymph nodes of Stage II patients (whose lymph nodes otherwise appear to be not involved with cancer), the outlook is similar to that of Stage III patients. Patients without this so-called micrometastasis have a very favorable prognosis. Further research is needed, however, before PCR can be used in widespread practice.
• In patients with a history of or active colon cancer, follow-up measuring of blood CEA levels may be helpful in detecting recurrence of the cancer and effectiveness of treatments.

Defective P53 Gene. The presence of a defective p53 gene is a marker for very poor prognosis in patients with advanced colon cancer. In its normal state, the gene is important for regulation of cell growth. Testing for this abnormality, however, is not widely done because it is not clear how to use this information.

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Other Tumor Markers. Other tumor markers under investigation include a protein called GLUT1, cancer antigen 19-9 (CA 19-9), matrix metalloproteinase-9 (MMP-9) RNA, HER-2/neu oncoprotein, transforming growth factor beta-1 (TGF-beta-1), and CD44. However, their role is unknown and they should not be used outside the setting of a clinical study.

Click the icon to see an image of drawing blood for culture.

Sentinel Node Biopsy