Table of ContentsView AllTable of ContentsPurposeRisks and ContraindicationsBefore the TestDuring the TestAfter the TestInterpreting ResultsFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
Purpose
Risks and Contraindications
Before the Test
During the Test
After the Test
Interpreting Results
Frequently Asked Questions
Various tools are used to monitor cancer progression and treatment response. For some cancers,tumor marker blood tests, such as the CA 15-3 blood test, can be indicative of tumor changes.
CA 15-3 is one of several substances classified astumor markers, which may increase as a malignancy progresses and decrease as a tumor gets smaller in response tocancer therapy. It is one of several tumor markers used to monitor people withstage 4 breast cancer(also known asmetastaticbreast cancer).While someoncologists(specialists who treat cancer) will use the test as a way to detectbreast cancer recurrence, it is not recommended for this purpose.
Read on to learn more about the CA 15-3 blood test, what it does and what it means, and what you can expect when this test is ordered for you.
Where Breast Cancer Can Spread
CA 15-3 is an antigen that’s normally found in breast tissue. Antigens are proteins that identify a cell, acting as its “signature.”
While the CA 15-3 antigen does not cause cancer, the level can increase as cancer cells multiply. The number of CA 15-3 antigens will increase with a tumor’s growth.
That said, not all breast cancers produce CA 15-3 antigens. This is especially true with early-stage breast cancer. Fewer than half of patients with early-stage breast cancer will show elevations in CA 15-3 values and up to 80% of people with metastatic breast cancer (breast cancer in late stages that has spread) will have increased CA 15-3 levels.
These dynamics make the CA 15-3 useful for monitoring stage 4 breast cancer or secondary tumors in other parts of the body.
Your oncologist may order a CA 15-3 test for one of these two reasons:
Verywell / Theresa Chiechi
Limitations: Sensitivity and Specificity
Although the CA 15-3 test is valuable for monitoring breast cancer, it is less reliable when used for cancer screening. This is partly because the CA 15-3 is not a highly sensitive test and it’s not specific to breast cancer.
Other benign and malignant conditions can also cause increases, such as:
And pregnancy can increase CA 15-3 levels.
The CA 15-3 test also has low sensitivity because breast cancer doesn’t always cause it to increase. In fact, according to a 2015 study from Germany, the CA 15-3 test has a sensitivity of only 55.6% when used to diagnose metastatic breast cancer.
Due to its potential forfalse-positive results(results that read as positive for cancer when there is no cancer), the American Society of Clinical Oncologists (ASCO) advises against the use of tumor marker tests to screen for new or recurring breast cancer.
Routinemammogramsare considered the frontline tool for breast cancer screening in most countries.
There are few risks associated with the CA 15-3 test. The test requires a blood draw, which may cause mild pain, redness, or bruising. Light-headedness and fainting may also occur.
Less commonly, the blood draw may cause ahematoma, which is an accumulation of blood under the skin. Most small hematomas go away on their own; larger ones may require treatment.
Infection is rare following a blood draw if standard health precautions are taken.
Measuring CA 15-3 requires a blood test typically performed along with a complete blood count (CBC),liver functions tests, andkidney function tests. There are no preparations needed for any of these tests.
Timing
The blood draw takes only a few minutes. Depending on the registration and the waiting time, your appointment can take 30–90 minutes.
Location
What to Wear
You should choose a top that has either short sleeves or sleeves that can be easily rolled up. If you plan to return to work after the test, you may want to wear long sleeves to cover the bandage or puncture mark on your arm.
Food and Drink
There are no food or drink restrictions for the CA 15-3 test.
If you have small veins, it often helps to drink a couple of glasses of water before the test. Doing so won’t affect the results, but may plump your veins and make the blood draw easier.
Medications That Alter Results
Certain medications and supplements can interfere with the CA 15-3 test. Among them isbiotin(also known as vitamin B7, vitamin B8, vitamin H, or coenzyme R). The CA 15-3 test relies on biotin to bind to the CA 15-3 antigen and may be affected if too much biotin is consumed.
While the recommended daily intake of biotin is unlikely to cause any harm, high-dose biotin supplements may trigger false-negative readings. Stop taking any supplement containing more than 0.03 milligrams of biotin 72 hours before the test.
In addition, the targeted cancer drug Afinitor (everolimus) may cause paradoxical effects. The drug may cause CA 15-3 levels to rise when treatment is working (resulting in a false-positive result) or drop when treatment is failing (resulting in a false-negative result that appears negative when it is actually positive).
You should tell thephlebotomistif you are on Afinitor so a notation can be made for the reviewingpathologist.
Cost and Health Insurance
The test doesn’t usually require preauthorization (the insurance carrier having to approve the test before it is performed), but you may be limited as to how many tests you can take each year. Check your policy or call your health insurer for details.
If you are uninsured or struggling with treatment costs, ask your oncologist if there are anyfinancial assistance programsyou qualify for. You should also contact theCancer Financial Assistance Coalition (CFAC), a group of national organizations that provide financial help to people with cancer.
What to Bring
You will need to bring a form of ID, your health insurance card, and either a credit card or check to cover any out-of-pocket expenses. Find out which form of payment the office accepts before you go to your appointment.
When you arrive at the lab, you will be asked to sign in and complete a registration form. Many labs will ask you to pay yourcoinsurance or co-paycosts in advance; others will bill you later. A consent form may also be provided.
Throughout the Test
Once the vein is selected, they will place a tourniquet around your upper arm and ask that you make a fist. You may be asked to pump your fist several times if your veins are small. The site is then swabbed with an alcohol pad.
You will feel a small prick as the needle is inserted. For the CA 15-3 test, the phlebotomist will need to obtain a minimum of 0.3 milliliters of blood. The vacuum-sealed test tube will usually have a red top or a gel barrier.
Once the needle is withdrawn, a cotton ball or gauze is placed on your arm until the bleeding stops. The phlebotomist then applies an adhesive bandage over the puncture wound.
Post-Test
You should be able to leave shortly after your test as long as you are not bleeding or feeling woozy. You can then continue your day as usual.
You may feel sore or develop redness or bruising at the puncture site. These issues will usually resolve on their own without treatment. If needed, you can take Tylenol (acetaminophen) to help alleviate the pain.
If you develop a small lump, you can apply a cold compress on your arm for 20 minutes several times a day to relieve the swelling. Do not apply ice directly to the skin or leave it on for longer.
Call your healthcare provider if you develop any signs of infection after a blood draw, including a high fever and persistent or worsening pain, swelling, or tenderness at the puncture site.
The results of your test should be sent to your oncologist within three to five working days. The report will include a reference range outlining the normal and abnormal CA 15-3 levels. This is based on the expected values within a population and can vary slightly from one lab to the next.
Generally speaking, a CA 15-3 value of 30 units per millimeter (U/mL) or less is considered normal.With that being said, a single value is generally not as helpful in diagnosis as serial values, in which your results are routinely measured during the course of treatment.
Your CA 15-3 level must be evaluated in conjunction with a physical examination, diagnostic imaging, and other blood tests.
Higher CA 15-3 levels typically correspond with more advanced stages of breast cancer.The highest levels tend to be seen in metastatic breast cancer, particularly when the liver or bone is involved. However, CA 15-3 levels can be low or normal even in advanced disease since not all breast cancers produce CA 15-3.
Sometimes CA 15-3 levels can be abnormally elevated during the first four to six weeks of new cancer therapy. Any treatment that disrupts a tumor can cause a temporary rise in tumor markers. To avoid misinterpretation, the CA 15-3 test should be performed at least two to three months after starting a new treatment.
It is important to note that when CA 15-3 levels are elevated with benign conditions, the levels tend to remain stable. It is only when levels rise that further investigation may be warranted.
If your CA 15-3 results are elevated, your oncologist will likely order additional tests. If the elevation is minimal, the healthcare provider may take a watch-and-wait approach and order a repeat test several weeks later.
If elevation persists or increases, your healthcare provider may order additional testing.
This may include:
Summary
While a CA 15-3 blood test might be helpful to your doctor as part of the bigger picture, it is not used alone to monitor your response to treatment. Because of all of the factors that can cause fluctuating antigen levels, it’s best to see this with other monitoring tests.
It is most effective in monitoring advanced breast cancer and its response to treatment, but even with metastatic breast cancer, this is not the only evaluation tool available.
A Word From Verywell
You might experience stress or anxiety when you’re having blood tests to monitor metastatic breast cancer, especially if you have a sudden rise in a tumor marker. However, it is important to remember that the CA 15-3 provides only a glimpse of what is going on. Results should be examined in the context of your health and other diagnostic evaluations.
Having a temporary increase in CA 15-3 levels does not necessarily mean that your cancer is spreading. Along those same lines, a temporary decrease does not necessarily mean that the cancer is disappearing.
Frequently Asked QuestionsA CA 15-3 level often is associated with breast cancer.It may indicate that cancer that you were treated for has returned. Non-cancer-related explanations can include endometriosis, pelvic inflammatory disease, chronic hepatitis, and more. Your doctor will do more tests to explore the underlying cause of the elevated marker.Learn MoreHow Breast Cancer Is DiagnosedA CA 15-3 measure that’s less than 30 units per milliliter (U/mL) is considered normal.Learn MoreWhat You Should Know About Cancerous TumorsBoth of these test for cancer antigens. However, CA 27.29 and CA 15-3 measure different tumor markers. While their results are often related, they are different and should not be used interchangeably.Learn MoreWhat Is the Cancer Antigen 27.29?While it may mean your cancer is responding to treatment, advanced breast cancer can have low tumor markers, specifically, low CA 15-3 levels. Doctors can use them as one piece of information among many. Your doctor will be able to provide you with more information based on other tests they do.Learn MoreOverview of Tumor Markers
A CA 15-3 level often is associated with breast cancer.It may indicate that cancer that you were treated for has returned. Non-cancer-related explanations can include endometriosis, pelvic inflammatory disease, chronic hepatitis, and more. Your doctor will do more tests to explore the underlying cause of the elevated marker.Learn MoreHow Breast Cancer Is Diagnosed
A CA 15-3 level often is associated with breast cancer.It may indicate that cancer that you were treated for has returned. Non-cancer-related explanations can include endometriosis, pelvic inflammatory disease, chronic hepatitis, and more. Your doctor will do more tests to explore the underlying cause of the elevated marker.
Learn MoreHow Breast Cancer Is Diagnosed
A CA 15-3 measure that’s less than 30 units per milliliter (U/mL) is considered normal.Learn MoreWhat You Should Know About Cancerous Tumors
A CA 15-3 measure that’s less than 30 units per milliliter (U/mL) is considered normal.
Learn MoreWhat You Should Know About Cancerous Tumors
Both of these test for cancer antigens. However, CA 27.29 and CA 15-3 measure different tumor markers. While their results are often related, they are different and should not be used interchangeably.Learn MoreWhat Is the Cancer Antigen 27.29?
Both of these test for cancer antigens. However, CA 27.29 and CA 15-3 measure different tumor markers. While their results are often related, they are different and should not be used interchangeably.
Learn MoreWhat Is the Cancer Antigen 27.29?
While it may mean your cancer is responding to treatment, advanced breast cancer can have low tumor markers, specifically, low CA 15-3 levels. Doctors can use them as one piece of information among many. Your doctor will be able to provide you with more information based on other tests they do.Learn MoreOverview of Tumor Markers
While it may mean your cancer is responding to treatment, advanced breast cancer can have low tumor markers, specifically, low CA 15-3 levels. Doctors can use them as one piece of information among many. Your doctor will be able to provide you with more information based on other tests they do.
Learn MoreOverview of Tumor Markers
12 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Ca 15-3: reference range, interpretation, collection and panels.https://emedicine.medscape.com/article/2087491-overview#a2American Association for Clinical Chemistry.CA 15-3.Rafey M, Akhtar K, Rab A, et al.Serum Ca 15-3: A useful tumor marker in the prognostication of locally advanced breast cancer.Ann Woman Child Health. 2017;3(4):A50-A51. doi:10.21276/awch.1782Buonomo B, Noli SA, Santini A, Alviggi C, Peccatori FA. Can we trust tumour markers in pregnancy after breast cancer? A case of elevated CA 15-3 in the third trimester of pregnancy normalising after delivery. Ecancermedicalscience. 2019;13:979.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946420/Stieber P, Nagel D, Blankenburg I, et al.Diagnostic efficacy of CA 15-3 and CEA in the early detection of metastatic breast cancer-A retrospective analysis of kinetics on 743 breast cancer patients.Clin Chim Acta. 2015;448:228-31. doi:10.1016/j.cca.2015.06.022Runowicz CD, Leach CR, Henry NL, et al.American Cancer Society/American Society of Clinical Oncology Breast Cancer Survivorship Care Guideline.J Clin Oncol. 2016;34(6):611-35. doi:10.1200/JCO.2015.64.3809US Food & Drug Administration.The FDA warns that biotin may interfere with lab tests: FDA safety communication.Orlandi A, Dio CD, Calegari MA, Barone C.Paradox CA 15-3 increase in metastatic breast cancer patients treated with everolimus: a change of paradigm in a case series.Biomark Med. 2016;10(11):1191-1195. doi:10.2217/bmm-2016-0142Vachani C. OncoLink. University of Pennsylvania.Patient Guide to Tumor Markers.Nieder C, Dalhaug A, Haukland E, et al.Prognostic impact of the tumor marker CA 15-3 in patients with breast cancer and bone metastases treated with palliative radiotherapy.J Clin Med Res. 2017;9(3):183-7. doi:10.14740/jocmr2653wUniversity of Rochester Medical Center.CA 15-3.Lin D, Genzen J. Comparison of breast cancer tumor marker test results: A retrospective analysis of paired CA 15-3 and CA 27.29 testing at a national reference laboratory. Am J Clin Path. 2017;147(S2):S156 doi:10.1093/ajcp/aqw191.009https://academic.oup.com/ajcp/article/147/suppl_2/S156/3059225Additional ReadingShao Y, Zianfu S, Yaning H et al.Elevated levels of serum tumor markers CEA and CA15-3 are prognostic parameters for different molecular subtypes of breast cancer.PLoS One. 2015;10(7):e0133830. doi:10.1371/journal.pone.0133830
12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Ca 15-3: reference range, interpretation, collection and panels.https://emedicine.medscape.com/article/2087491-overview#a2American Association for Clinical Chemistry.CA 15-3.Rafey M, Akhtar K, Rab A, et al.Serum Ca 15-3: A useful tumor marker in the prognostication of locally advanced breast cancer.Ann Woman Child Health. 2017;3(4):A50-A51. doi:10.21276/awch.1782Buonomo B, Noli SA, Santini A, Alviggi C, Peccatori FA. Can we trust tumour markers in pregnancy after breast cancer? A case of elevated CA 15-3 in the third trimester of pregnancy normalising after delivery. Ecancermedicalscience. 2019;13:979.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946420/Stieber P, Nagel D, Blankenburg I, et al.Diagnostic efficacy of CA 15-3 and CEA in the early detection of metastatic breast cancer-A retrospective analysis of kinetics on 743 breast cancer patients.Clin Chim Acta. 2015;448:228-31. doi:10.1016/j.cca.2015.06.022Runowicz CD, Leach CR, Henry NL, et al.American Cancer Society/American Society of Clinical Oncology Breast Cancer Survivorship Care Guideline.J Clin Oncol. 2016;34(6):611-35. doi:10.1200/JCO.2015.64.3809US Food & Drug Administration.The FDA warns that biotin may interfere with lab tests: FDA safety communication.Orlandi A, Dio CD, Calegari MA, Barone C.Paradox CA 15-3 increase in metastatic breast cancer patients treated with everolimus: a change of paradigm in a case series.Biomark Med. 2016;10(11):1191-1195. doi:10.2217/bmm-2016-0142Vachani C. OncoLink. University of Pennsylvania.Patient Guide to Tumor Markers.Nieder C, Dalhaug A, Haukland E, et al.Prognostic impact of the tumor marker CA 15-3 in patients with breast cancer and bone metastases treated with palliative radiotherapy.J Clin Med Res. 2017;9(3):183-7. doi:10.14740/jocmr2653wUniversity of Rochester Medical Center.CA 15-3.Lin D, Genzen J. Comparison of breast cancer tumor marker test results: A retrospective analysis of paired CA 15-3 and CA 27.29 testing at a national reference laboratory. Am J Clin Path. 2017;147(S2):S156 doi:10.1093/ajcp/aqw191.009https://academic.oup.com/ajcp/article/147/suppl_2/S156/3059225Additional ReadingShao Y, Zianfu S, Yaning H et al.Elevated levels of serum tumor markers CEA and CA15-3 are prognostic parameters for different molecular subtypes of breast cancer.PLoS One. 2015;10(7):e0133830. doi:10.1371/journal.pone.0133830
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Ca 15-3: reference range, interpretation, collection and panels.https://emedicine.medscape.com/article/2087491-overview#a2American Association for Clinical Chemistry.CA 15-3.Rafey M, Akhtar K, Rab A, et al.Serum Ca 15-3: A useful tumor marker in the prognostication of locally advanced breast cancer.Ann Woman Child Health. 2017;3(4):A50-A51. doi:10.21276/awch.1782Buonomo B, Noli SA, Santini A, Alviggi C, Peccatori FA. Can we trust tumour markers in pregnancy after breast cancer? A case of elevated CA 15-3 in the third trimester of pregnancy normalising after delivery. Ecancermedicalscience. 2019;13:979.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946420/Stieber P, Nagel D, Blankenburg I, et al.Diagnostic efficacy of CA 15-3 and CEA in the early detection of metastatic breast cancer-A retrospective analysis of kinetics on 743 breast cancer patients.Clin Chim Acta. 2015;448:228-31. doi:10.1016/j.cca.2015.06.022Runowicz CD, Leach CR, Henry NL, et al.American Cancer Society/American Society of Clinical Oncology Breast Cancer Survivorship Care Guideline.J Clin Oncol. 2016;34(6):611-35. doi:10.1200/JCO.2015.64.3809US Food & Drug Administration.The FDA warns that biotin may interfere with lab tests: FDA safety communication.Orlandi A, Dio CD, Calegari MA, Barone C.Paradox CA 15-3 increase in metastatic breast cancer patients treated with everolimus: a change of paradigm in a case series.Biomark Med. 2016;10(11):1191-1195. doi:10.2217/bmm-2016-0142Vachani C. OncoLink. University of Pennsylvania.Patient Guide to Tumor Markers.Nieder C, Dalhaug A, Haukland E, et al.Prognostic impact of the tumor marker CA 15-3 in patients with breast cancer and bone metastases treated with palliative radiotherapy.J Clin Med Res. 2017;9(3):183-7. doi:10.14740/jocmr2653wUniversity of Rochester Medical Center.CA 15-3.Lin D, Genzen J. Comparison of breast cancer tumor marker test results: A retrospective analysis of paired CA 15-3 and CA 27.29 testing at a national reference laboratory. Am J Clin Path. 2017;147(S2):S156 doi:10.1093/ajcp/aqw191.009https://academic.oup.com/ajcp/article/147/suppl_2/S156/3059225
Ca 15-3: reference range, interpretation, collection and panels.
https://emedicine.medscape.com/article/2087491-overview#a2
American Association for Clinical Chemistry.CA 15-3.
Rafey M, Akhtar K, Rab A, et al.Serum Ca 15-3: A useful tumor marker in the prognostication of locally advanced breast cancer.Ann Woman Child Health. 2017;3(4):A50-A51. doi:10.21276/awch.1782
Buonomo B, Noli SA, Santini A, Alviggi C, Peccatori FA. Can we trust tumour markers in pregnancy after breast cancer? A case of elevated CA 15-3 in the third trimester of pregnancy normalising after delivery. Ecancermedicalscience. 2019;13:979.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946420/
Stieber P, Nagel D, Blankenburg I, et al.Diagnostic efficacy of CA 15-3 and CEA in the early detection of metastatic breast cancer-A retrospective analysis of kinetics on 743 breast cancer patients.Clin Chim Acta. 2015;448:228-31. doi:10.1016/j.cca.2015.06.022
Runowicz CD, Leach CR, Henry NL, et al.American Cancer Society/American Society of Clinical Oncology Breast Cancer Survivorship Care Guideline.J Clin Oncol. 2016;34(6):611-35. doi:10.1200/JCO.2015.64.3809
US Food & Drug Administration.The FDA warns that biotin may interfere with lab tests: FDA safety communication.
Orlandi A, Dio CD, Calegari MA, Barone C.Paradox CA 15-3 increase in metastatic breast cancer patients treated with everolimus: a change of paradigm in a case series.Biomark Med. 2016;10(11):1191-1195. doi:10.2217/bmm-2016-0142
Vachani C. OncoLink. University of Pennsylvania.Patient Guide to Tumor Markers.
Nieder C, Dalhaug A, Haukland E, et al.Prognostic impact of the tumor marker CA 15-3 in patients with breast cancer and bone metastases treated with palliative radiotherapy.J Clin Med Res. 2017;9(3):183-7. doi:10.14740/jocmr2653w
University of Rochester Medical Center.CA 15-3.
Lin D, Genzen J. Comparison of breast cancer tumor marker test results: A retrospective analysis of paired CA 15-3 and CA 27.29 testing at a national reference laboratory. Am J Clin Path. 2017;147(S2):S156 doi:10.1093/ajcp/aqw191.009
https://academic.oup.com/ajcp/article/147/suppl_2/S156/3059225
Shao Y, Zianfu S, Yaning H et al.Elevated levels of serum tumor markers CEA and CA15-3 are prognostic parameters for different molecular subtypes of breast cancer.PLoS One. 2015;10(7):e0133830. doi:10.1371/journal.pone.0133830
Meet Our Medical Expert Board
Share Feedback
Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit
Was this page helpful?
Thanks for your feedback!
What is your feedback?OtherHelpfulReport an ErrorSubmit
What is your feedback?
