Does the CA 15-3 tumor marker test fluctuate for others?

I have not heard of this blood test. Can you tell me what it is used for.

I’m on Kisqali and Fulvestrant, too. My blood test is the CA 27-29.

Hi Marion, I was diagnosed with MBC using the CA15 and ca27 blood tests. One was over 5500, and the other was 3200. I had switched oncologists and the new doctor wanted to get an idea if there was any indication of cancer. Since my numbers were so high a pet scan was ordered. Much to my surprise the pet scan revealed cancer in every bone except my forearms, hands, calves and feet. The cancer had also spread to my lungs. While the CA tests are good for identifying that cancer is present, many doctors choose not to use them as it really doesn’t tell you anything other that there is cancer. Pet scans , MRI, Ct scans seem to be the most preferred tests as they give exact locations of Mets/lesions. These tests will also show if the cancer is shrinking which means that the medication cocktail that you are on is working or not. Many doctors want you have them every 3 months . Best of luck to you! Melissa

It's completely normal for tumor marker levels to have some fluctuation from month to month, and many people in the community have similar experiences with CA 15-3 testing. Small changes like the 5-point variations you're describing can happen for various reasons and don't necessarily indicate changes in your treatment response. Your oncology team will be looking at trends over time rather than individual test results, so it's worth discussing these fluctuations with them to get their perspective on your specific situation.

Yes my Dr. uses that test and also the CEA just because the markers flowed up and down I was told that it doesn’t really mean that there’s any kind of spread. It’s why my Dr. believes in the Pet-Scan than the markers. Sometimes they show an increase cause there’s extra cancer cells around of course as to how high they are. Mine went of 2000 so I’m back on chemo for now. In fact going for my third infusion on Monday. Oh what fun can’t wait! And my husband and are desperately trying to move. It just seems u take a step forward than 2 steps back. Anytime u want to can write me Or I’ll give u my phone number. Be well. Mary