Carcinoembryonic antigen (CEA) is a substance monitored in individuals with cancer. This article clarifies how CEA levels can fluctuate during chemotherapy.
What CEA Is and Why It’s Monitored
Carcinoembryonic antigen (CEA) is a protein normally produced during fetal development. In healthy adults, CEA levels are typically very low, generally between 0 and 3 nanograms per milliliter (ng/mL) for non-smokers. Levels can be elevated in certain cancers, including those of the colon, rectum, lung, breast, pancreas, and stomach.
CEA functions as a “tumor marker,” produced by cancer cells or by normal cells in response to cancer. Healthcare providers use CEA measurements primarily to monitor known cancers, assess treatment effectiveness, and detect cancer recurrence. CEA testing is not used for initial cancer screening or diagnosis, as elevated levels can occur due to various non-cancerous conditions.
The Nature of CEA Fluctuations During Chemotherapy
CEA levels often fluctuate during chemotherapy. An initial, temporary rise, sometimes called a “CEA flare,” can occur early in treatment. This happens as chemotherapy destroys cancer cells, releasing CEA into the bloodstream, and can indicate effective treatment.
Ideally, successful chemotherapy leads to a general downward trend in CEA levels, indicating cancer response. A significant decrease in CEA levels during therapy often suggests a positive response. However, minor fluctuations or plateaus can occur due to biological variability or cyclical chemotherapy administration.
A sustained rise in CEA levels during or after chemotherapy may indicate disease progression or treatment resistance, prompting further investigation by healthcare providers.
Factors Influencing CEA Levels Beyond Cancer Activity
CEA levels are not exclusively indicative of cancer activity and can be influenced by several non-cancerous factors. Smoking is a common cause of elevated CEA levels, with current or heavy smokers often having higher baseline levels, sometimes up to 5 ng/mL. Changes in smoking habits can also affect these readings.
Inflammation from various conditions can also temporarily raise CEA levels, including infections, inflammatory bowel diseases like Crohn’s disease or ulcerative colitis, pancreatitis, and certain liver conditions such as cirrhosis. Post-operative inflammation can also contribute to temporary elevations.
Some benign conditions affecting the liver, lungs, or digestive system, such as gastritis, peptic ulcers, diverticulitis, or chronic obstructive pulmonary disease (COPD), can lead to mild CEA elevations. Minor differences in laboratory techniques or equipment can result in slight variations between test results, highlighting the importance of consistent testing methods.
How Healthcare Providers Interpret CEA Trends
Healthcare providers rarely rely on a single CEA reading. Instead, they carefully consider the overall trend of CEA levels over time. A consistent pattern of increasing or decreasing levels holds more significance than any isolated measurement.
CEA levels are always interpreted within the broader clinical context of the patient. This includes evaluating symptoms, conducting physical examinations, and reviewing results from other diagnostic tests, such as imaging scans (CT, MRI, PET scans) or biopsies. This comprehensive approach helps differentiate between fluctuations caused by cancer activity and those due to other factors.
Each patient’s pre-treatment CEA level serves as an individual baseline against which subsequent measurements are compared. This personalized approach allows the medical team to track changes relevant to that specific patient’s condition.
Patients should discuss their CEA results with their oncology team, as they are equipped to interpret the data within the full clinical picture and make informed decisions about ongoing treatment. Self-interpretation of minor fluctuations should be avoided to prevent unnecessary anxiety.