CA 15-3 — The Breast Cancer Monitoring Companion
CA 15-3 is a protein that certain cancer cells shed into the bloodstream. It is measured through a simple venous blood draw and is primarily used to keep track of breast cancer — how it is responding to treatment, whether it is progressing, and whether it is coming back. While it is most closely tied to breast cancer, CA 15-3 can also be influenced by other cancers (liver, colorectal, ovarian, pancreatic, lung, gastric) and even some non-cancerous conditions.
Why Test CA 15-3 Test?
If you have a confirmed breast cancer diagnosis, CA 15-3 becomes a real workhorse. It helps monitor treatment effectiveness, assess disease progression, detect recurrence, and evaluate whether cancer may have spread. It is elevated in up to 70% of patients with metastatic breast cancer, making it one of the more reliable tracking tools in that setting.
What Do High CA 15-3 Test Levels Mean?
Elevated CA 15-3 (above 30 U/mL) may signal active, advanced, or recurrent breast cancer. But the picture is rarely that simple — other cancers and non-malignant conditions like liver cirrhosis, benign breast disease, or inflammation can also be behind a high reading. A single elevated value is a prompt for investigation, not a verdict. It needs to be interpreted alongside imaging and clinical findings.
What Do Low CA 15-3 Test Levels Mean?
Normal CA 15-3 levels (typically below 30 U/mL) suggest no active cancer or stable disease in most cases. A declining trend during treatment is generally great news — it usually means the therapy is working. That said, not all breast cancers produce CA 15-3, so normal levels do not completely rule things out.
Symptoms to Watch For
- A lump or thickening in the breast
- Changes in breast size or shape
- Skin changes on the breast such as dimpling
- Nipple discharge or inversion
- Bone pain or unexplained weight loss in advanced disease
Who Should Get Tested?
- Patients with a confirmed breast cancer diagnosis
- Women undergoing treatment who need progress monitoring
- Patients in remission being watched for recurrence
- Anyone with symptoms suggesting possible metastasis
- Those with previously abnormal CA 15-3 values needing follow-up
How to Prepare for Your Test
No special prep needed. Just bring valid ID to your appointment.
Order Your Blood Test
Test your CA 15-3 Test levels with an accredited Swedish laboratory. Results within days, reviewed by Wellth.
Frequently Asked Questions
Is CA 15-3 used for breast cancer screening?
Can CA 15-3 be elevated in conditions other than breast cancer?
What does a rising CA 15-3 level mean?
How often should CA 15-3 be tested?
Reviewed by
Wellth Team
Wellth
Our content is written and reviewed by Wellth, and fact-checked against peer-reviewed research and current Swedish clinical guidelines.
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The information on this page is provided for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment. Wellth provides health information and testing services but is not a substitute for clinical care. Always consult a qualified healthcare provider if you have questions about a medical condition. If you are experiencing severe or urgent symptoms, contact your doctor or call 1177 Vårdguiden. Blood test results should be interpreted by a qualified healthcare professional in the context of your complete medical history.