Normal CEA levels but still have colon cancer

Carcinoembryonic antigen (CEA) is a protein often measured in blood to monitor certain cancers, particularly colorectal cancer. Normal CEA levels typically range from 0 to 2.5 ng/mL in non-smokers and up to 5 ng/mL in smokers, though exact ranges may vary slightly by lab.
However, it is possible to have normal CEA levels and still have colon cancer because:
Early-Stage Cancer: CEA levels are often normal in early-stage colon cancer (Stage I or II) as the tumor may not produce enough CEA to elevate blood levels.
Non-CEA-Producing Tumors: Some colon cancers do not produce significant amounts of CEA, even in advanced stages, due to the tumor's biology.
Individual Variation: CEA production varies among individuals, and some patients with colon cancer never show elevated CEA.
Other Factors: Conditions like inflammation, liver disease, or smoking can influence CEA levels, potentially masking cancer-related changes.
Key Point: Normal CEA does not rule out colon cancer. Diagnosis relies on imaging (e.g., colonoscopy, CT scans), biopsies, and other clinical findings. CEA is more useful for monitoring treatment response or detecting recurrence in patients with known CEA-producing tumors, but even then other tests such as CTDNA are more specific and sensitive. In my opinion only CEA levels of 20 or more are meaningful. Suggest you discuss this with your oncologist

Before my cancer colon surgery, my CEA was 1.7. Since my surgery, my CEA has ranged from 3 to 1.9 (9 years). My tumor was stage one so that may be why my CEA was the lowest before surgery.

Also, inflammation from the surgery could cause a slight rise in CEA. How is your oncologist monitoring following the surgery?