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Normal ranges of a tumor marker?

30 July 2011

Anne Kenworthy writes:

I was just turned onto this site by a friend. I am currently battling cancer. In April, My CEA (cancer marker) was at 22. Today, in the last week of July, it is at 1.9. My oncologist told me this was the “normal” range; was pleased and refused to enlighten me beyond that. What does it mean to have a “normal” cancer marker? Does this mean we all walk around with some level of “cancer” in our bodies and this is the acceptable level? What’s going on?

Hi Anne,

I am sorry to hear of your cancer battle, but I am pleased to hear that an experienced oncologist was pleased at your current biomarkers. However, I am not pleased that he was not willing to discuss exactly what that means. You hit on a very interesting topic that I would like to explore with two articles.

CEA, or Carcinoembryonic Antigen, is a protein that is normally produced during fetal development. Certain types of tumors can begin to produce CEA in adults, and it is useful as a tumor marker because the progress of cancer treatment can be tracked by levels of CEA. However, nothing is absolute in biology, and some level of CEA is not uncommon in healthy adults.

According to the website of the National Institutes of Health, normal levels of CEA in adults is 0 to 2.5 micrograms per liter. For smokers, the range is 0 to 5.0 ug/L. (1) Those numbers were derived from testing the blood of many, many healthy individuals, and it would be incorrect to say that a level of CEA in that range is necessarily indicative of cancer.

In a broader sense, tumor biomarkers are usually proteins that are absent or low in people without cancer. There are many tumor markers used for various types and subtypes of cancer, and they all have their nuances and limitations. A tumor biomarker is not the golden standard to whether or not someone has cancer. A tumor biopsy combined with a trained pathologist and a somewhat low-tech (but still very nice) microscope is actually the golden standard of diagnosis. But, that process still requires one to know where tumors are, and for the tumors to be large enough to get a needle biopsy.

The disease will never be cured for some cancer patients, but they will live for decades with the disease without quick progression. Some will eventually die with the disease, not of it, and live fairly normal lives thereafter.

But is it possible that all of us have some level of cancer? Yes. I will explore this paradox in next week’s article. Within the scientific community, cancer is being seen more and more as a “natural” hiccup of physiology.


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