Stage 1 colon cancer is an early form of the disease where malignant cells have grown through the initial layers of the colon wall but have not spread to nearby lymph nodes or distant parts of the body. The carcinoembryonic antigen (CEA) test is a blood analysis that measures a protein sometimes produced by cancer cells.
The Role of CEA in Colon Cancer Diagnosis
The CEA test is not recommended as a primary screening tool or the sole method for initially diagnosing colon cancer. This is because the test lacks sufficient sensitivity; a person can have early-stage colon cancer and still exhibit normal CEA levels. It also lacks specificity, as elevated CEA levels can occur due to various non-cancerous conditions. A definitive diagnosis of stage 1 colon cancer relies on more direct methods, such as a colonoscopy for visual inspection and a biopsy of suspicious tissue. A pathologist then examines the tissue to confirm cancer and determine its exact stage.
Typical CEA Levels in Early-Stage Colon Cancer
Many individuals diagnosed with stage 1 colon cancer have CEA levels within the normal range. For non-smokers, a typical CEA level is below 2.5 nanograms per milliliter (ng/mL). For smokers, a level under 5.0 ng/mL may be considered normal. This occurs because many early-stage tumors are small and may not produce enough carcinoembryonic antigen to cause a detectable elevation. Therefore, a normal CEA test result does not rule out early-stage colon cancer.
Using CEA for Post-Treatment Monitoring
The CEA test’s primary value for stage 1 colon cancer patients is post-treatment monitoring. After successful treatment, like surgical tumor removal, a baseline CEA level is established, typically a few weeks after the procedure, when it should ideally return to normal. Doctors then use serial CEA tests, often every few months, to monitor for cancer recurrence. A rising trend in CEA levels over consecutive tests can indicate the cancer may have returned, sometimes before other symptoms appear. Such an increase prompts further investigation, including imaging scans like CT scans, to pinpoint any potential recurrence.
Factors Influencing CEA Levels
Elevated CEA levels are not exclusively indicative of colon cancer and can be influenced by several non-cancerous conditions. Inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis, can lead to increased CEA readings due to inflammation in the digestive tract. Other benign conditions that may result in higher CEA levels include pancreatitis, an inflammation of the pancreas, and various liver diseases, such as cirrhosis or hepatitis. Peptic ulcers and lung infections are also known to cause temporary or mild elevations.