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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
Location: St. Louis MO
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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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Joined: Aug 24 2009
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Post Options Post Options   Thanks (1) Thanks(1)   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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CloudyNCool View Drop Down

Joined: May 05 2021
Location: Ottawa, ON
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CloudyNCool Quote  Post ReplyReply Direct Link To This Post Posted: Jun 14 2021 at 7:03pm
Thanks for this Liz. It's very helpful! 
I'm dealing with a recurrence and I've been anxiously looking for ways beyond scans to find another recurrence after I'm done this round of chemo. My oncologist says my cancer's very unusual and he'd like to know what's driving it. I don't qualify for Blueprint testing nor further genetic testing (I'm BRACA negative). He said those are for stage 4. He said mine was basal though when I asked. 
6/17 TNBC pT1c Grade 3 Lumpectomy, dose dence AC-P, rads/boosts (55yrs)

12/20 pT2(m), Grade 3
2/21 Bi mx
3 tumours:
HER2+ PR+(weak 1%) metaplastic features
PR+ (weak 1%)
4/21 TCH
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chrischan View Drop Down

Joined: Jul 04 2021
Location: los angeles
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chrischan Quote  Post ReplyReply Direct Link To This Post Posted: Jul 23 2021 at 1:35pm
Hi Liz,

What type of treatment are you on right now?  I also was diagnosed in 2018 stage 3 er/pr+ then in 2020 metastatized to liver and some changed to Her2+ and now new tumor in liver with triple negative.  So now we are waiting for the genomic testing to come back to see how to treat all 3 of these.

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