The Ca 125


“What is the Ca 125, and why does it rule my life?” one woman asked on an internet board I was reading. The Ca 125 is a tumor marker used for some cancers and especially for mine, which was endometrial. Usually, a blood sample is taken and the marker is measured in the blood. This is another one of those things that patients are cautioned not to obsess about, especially when taken out of context. But just as soon as you know yours, you start watching it like a hawk. You want it to go down below the cutoff for normal. Then you want it to stay there.

Like everything in real life, however, borders are difficult to pin down and things are not always what they seem.

Here’s how The National Cancer Institute defines tumor markers:

“Tumor markers are substances that are produced by cancer or by other cells of the body in response to cancer or certain benign (noncancerous) conditions. Most tumor markers are made by normal cells as well as by cancer cells; however, they are produced at much higher levels in cancerous conditions. These substances can be found in the blood, urine, stool, tumor tissue, or other tissues or bodily fluids of some patients with cancer.”

http://www.cancer.gov/cancertopics/factsheet/detection/tumor-markers

Note the careful use of words like “most” and “some” and “or,” not to mention the words “normal” and “however.” And as must be apparent from this description, a living human body can never be at zero, because something is always going on and normal cells are making this stuff in response to all kinds of activities. So you want to get the Ca 125 down to what is normal for you and then you want to be stable at that number.

For gynecological cancers, anything under something between 35 and 45 is normal. However, if you have a count in the 20s and it starts trending upwards, even if it's still under 35, you could be having a recurrence. Some patients have a count in the thousands when they are diagnosed. And yet, they get down to double digits. You can see how it can be harrowing even as it’s hardly precise.

When I was reading about this on a message board and saw one nervous party asking if she had to get down to zero, my favorite response was the one that explained it can’t be done and reassured her, “Your mail carrier is probably an 11.”

If you’ve got a female body, the Ca 125 can spike from pregnancy or even just from getting your period. It will probably spike from getting a gynecological cancer. But cruelly, you can have ovarian cancer and still have a Ca 125 within normal range. So it doesn't even help as a non-invasive screening because it lies too much. My own oncologist told me, “We are getting away from using it.” But he tests mine with every checkup. And I’m first in line to want to know what it is. My favorite nurse evades extensive discussion of it by saying, “We treat people, not numbers.”

But she also told me, when mine dropped into normal ranges by the third round of chemo, “That’s good for your prognosis.” And yes, hearing the word “prognosis” for the first time when it’s about you is just as chilling as you can imagine. Even if the news is good.

My number at diagnosis was 102. Believe it or not, that’s relatively low – especially for having turned out to be stage 4. For the past five years, since finishing treatment, I’ve bobbed between 10 and 12, which is real good and right in line with the hypothetical mail carrier mentioned above. I’m perfectly happy with it. I know of another endometrial 4 who bobs between 3 and 6, which is so pristine it’s just miraculous. But my nurse is right about numbers not being people. You are much more than your number and can never go wrong by believing in that. ###


Graphic by ianmacm, via Wikimedia Commons.

Further reading (we can hope for better tests):

A New Way to Interpret Ca125 Levels: Early Detection of Ovarian Cancer May Become Possible
By Denise Grady
New York Times, December 17, 2015

Blood Test Shows Promise as Alternative to Cancer Biopsy
By Gina Kolata
NYT April 19, 2015