Cancer Antigen 15-3
Other marker
CA 15-3
Cancer Antigen 15-3
A MUC1-derived tumour marker used mainly to monitor treatment response in metastatic breast cancer. Not a screening or diagnostic test.
PED Notes
No established relationship with anabolic steroid, peptide, or growth hormone use. It appears on some comprehensive panels and occasionally in male results, where a mildly raised value is far more likely to reflect a benign cause than cancer. The important point for anyone reading their own panel is that CA 15-3 is not a cancer screening test: levels are rarely raised in early or localised disease, so a normal value excludes nothing, and a mildly raised value in an asymptomatic person usually reflects benign liver or breast conditions rather than malignancy.
When high
A raised CA 15-3 is a finding for your doctor to interpret, not a result to act on alone.
Context determines everything:
- Mild elevation in an asymptomatic person -- commonly benign. Chronic liver disease, hepatitis, cirrhosis, benign breast conditions, and some autoimmune conditions all raise CA 15-3. Given that oral AAS carry real hepatotoxicity, a liver cause is worth checking
- Known breast cancer under treatment -- serial values track treatment response, and a rising trend can precede radiological progression by several months
- A single raised value means little -- the trend across serial measurements is what carries information
Appropriate next steps (physician-directed):
- Liver function tests and hepatic imaging -- to identify a benign hepatic cause
- Repeat in 4-8 weeks -- to establish whether the value is stable or rising
- Clinical examination and imaging -- guided by symptoms and risk factors, not by the number alone
Do not use CA 15-3 to screen yourself for cancer. Expert guidelines are explicit that it should be measured alongside imaging, clinical history, and examination, never in isolation.
Educational information, not medical advice. Nothing here is a prescription or a treatment plan, and it does not account for your history, medications or conditions. Use it to ask better questions: bring it to your doctor and decide together. Full disclaimer.
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range
VitalMetrics Range