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.
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range
VitalMetrics Range