Dear OncoLink "Ask The Experts,"
I have a question about the CEA (Carcinoembryonic Antigen) blood test. If this test is done to determine if cancer has returned in a patient, then why can't this test be done FIRST? I wonder if the CEA blood test could be used as a screening test to find colon cancer.
Timothy C. Hoops, MD, Clinical Assistant Professor of Medicine in the Gastroenterology Division at the University of Pennsylvania and Director of Gastroenterology at Penn Medicine at Radnor, responds:
Your question, and the concept you are proposing, is excellent and has been the Holy Grail of cancer screening. A simple blood test that would reliably identify patients with early cancers and rule out those who don't have it would be the perfect screening exam. Unfortunately, no such test exists. CEA is a protein that is found in several tissues, but in particular, it is in the colon. With cancer, this protein can be made in increased amounts and shed into blood. It has been carefully studied as a screening test. Unfortunately, it is not very sensitive. It frequently is normal and would miss cancers. Additionally, other factors can raise the CEA level, such as smoking. It is used in patients who have had cancers resected to look for recurrences with the hope that these will be found early enough to treat successfully. Even in this case, it is generally useful only when the initial cancer was CEA positive and the levels returned to normal after the initial treatment.
Ongoing research into other markers for cancer continue. Whoever finds such a test will have given us a great way to decrease the impact and number of deaths from colon cancer.