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Anyone doing CA15-3 Tumor Marker testing?

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LizBC View Drop Down

Joined: Feb 09 2014
Location: Victoria Canada
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    Posted: Mar 30 2021 at 12:51pm
I was diagnosed with TNBC in 2013 and thankfully the TNBC has not come back. I did have a recurrence in 2019 of two new breast cancers: HER2+ and also ER+PR+. They say bad things come in 3s, so I'm hoping this is the end of my cancer journey...Smile

I recently had a second opinion from a breast cancer specialist  around prevention and monitoring and he suggested that I monitor 6-monthly with a CA15-3 test. I was wondering if anyone has experience with this. My first oncologist said it was a waste of time because there's nothing I can do if it comes back. Any thoughts??

DX IDC TNBC Dec 2013 age 45, Stage 1, Grade 3, 1.7cm, 0/4Nodes, lumpectomy Jan 2013, DD AC x 4 and Paclitaxel x 4 Feb 2014, rads, BRCA neg
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cgiver View Drop Down

Joined: Mar 09 2021
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cgiver Quote  Post ReplyReply Direct Link To This Post Posted: Mar 31 2021 at 9:16am
here is a link I found. 

Seems to infer it wouldn’t be a standard test for non-metastatic BC
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123Donna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 123Donna Quote  Post ReplyReply Direct Link To This Post Posted: Apr 20 2021 at 10:52pm
Hi Liz,

Just saw your post.  When you had a recurrence, did you have other genetic testing?  Usually they now test for a full panel of genes vs BRCA only.  I know they are finding many more genes besides the BRCA gene that are associated with hereditary breast and ovarian cancers. 

Regarding tumor marking testing, I know many oncologists don't believe in them unless it's in the metastatic treatment setting.  When I was first diagnosed in 2009, my oncologist used the CA 27.29 tumor marker test.  My levels were always in the normal range, even when I found out I had a recurrence.  I had a friend who had metastatic ovarian cancer and the tumor marker tests were very accurate in determining when her cancer was active again.  It may be a valuable tool in the metastatic treatment setting, but not sure if it's highly effective as a screening tool (just my two cents).

What Is the Cancer Antigen 15-3 Blood Test?

A tumor marker test used to monitor metastatic breast cancer

The cancer antigen 15-3 (CA 15-3) biomarker test is used to monitor breast cancer. The CA 15-3 antigen is a protein released into the bloodstream by certain types of cancer. Although breast cancer is closely linked to the CA 15-3 antigen, it is associated with other cancerous and non-cancerous conditions as well.

CA 15-3 is one of several substances classified as tumor markers, which may increase as a malignancy progresses and decrease as a tumor responds to cancer therapy. The CA 15-3 is one of several tumor markers used to monitor people with stage 4 breast cancer (also known as metastatic breast cancer).1 While some oncologists will use the test to detect breast cancer recurrence, it is not endorsed for this use.


CA 15-3 is an antigen found normally in breast tissue. Antigens are Y-shaped proteins that identify a cell to the body, acting as its unique "signature."

While the CA 15-3 antigen does not cause cancer, it can increase in number as cancer cells rapidly divide. Because cancer cells do not undergo apoptosis (programmed cell death), the number of CA 15-3 antigens will increase in tandem with a tumor's growth.

With that said, not all breast cancers shed CA 15-3 antigens. This is especially true with early-stage breast cancer, in which fewer than half of patients will show elevations in CA 15-3 values. By contrast, up to 80% of people with metastatic breast cancer will have increased CA 15-3 levels.2

These dynamics make the CA 15-3 useful for monitoring stage 4 breast cancer in which a primary breast tumor has spread (metastasized), establishing secondary tumors in other parts of the body. If your oncologist orders a CA 15-3 test, it may be for one of two reasons:3

  • By regularly tracking your CA 15-3 values, the oncologist can assess how effectively a cancer treatment is working.
  • If CA 15-3 antigens rise over a certain level, it may indicate a worsening of the disease and warrant the investigation of metastasis in other parts of the body (most often the bone or liver).


Although the CA 15-3 test is valuable for monitoring breast cancer, it is less reliable when used for cancer screening. This is partly due to the fact that the CA 15-3 is specific to breast cancer but not exclusive to it.

DX IDC TNBC 6/09 age 49, Stage 1,Grade 3, 1.5cm,0/5Nodes,KI-67 48%,BRCA-,6/09bi-mx, recon, T/C X4(9/09)
11/10 Recur IM node, Gem,Carb,Iniparib 12/10,MRI NED 2/11,IMRT Radsx40,CT NED11/13,MRI NED3/15

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