Cancer biomarkers reference library
A comprehensive guide to understanding tumour markers, what they measure, and their role in cancer screening and monitoring.
Important Information About Cancer Screening
Cancer screening tests measure biomarkers that may be elevated in certain cancers. However, these tests are not diagnostic and should not be used as a substitute for professional medical advice.
- Elevated markers may be caused by non-cancerous conditions
- Normal results do not guarantee the absence of cancer
- Results should always be discussed with a qualified healthcare professional
- Further investigation may be required based on results
Understanding tumour markers
Tumour markers are substances—usually proteins—produced by cancer cells or by the body in response to cancer. They can be found in blood, urine, or tissue samples. While tumour markers can be helpful in detecting, diagnosing, and monitoring cancer, they are rarely definitive on their own and should always be interpreted alongside other diagnostic tests and clinical examination by a qualified healthcare professional.
PSA (Prostate-Specific Antigen)
Men's Health
A protein produced by the prostate gland. Elevated levels may indicate prostate cancer, benign prostatic hyperplasia (BPH), or prostatitis.
CA-125 (Cancer Antigen 125)
Women's Health
A protein found on the surface of ovarian cancer cells and some normal tissue. Elevated levels may suggest ovarian cancer or other conditions.
CEA (Carcinoembryonic Antigen)
General Cancer Marker
A protein involved in cell adhesion that can be elevated in various cancers. Originally thought to be specific to colon cancer but found in multiple cancer types.
AFP (Alpha-Fetoprotein)
Liver & Reproductive
A protein normally produced by the foetal liver and yolk sac. In adults, elevated levels may indicate liver cancer or certain germ cell tumours.
CA 19-9 (Carbohydrate Antigen 19-9)
Gastrointestinal
A carbohydrate tumour marker primarily associated with pancreatic and biliary tract cancers. Useful for monitoring treatment response.
CA 15-3 (Cancer Antigen 15-3)
Women's Health
A glycoprotein shed from breast cancer cells. Primarily used for monitoring metastatic breast cancer treatment rather than early detection.
FIT (Faecal Immunochemical Test)
Bowel Health
A stool-based test that detects hidden blood in faeces, which can be an early sign of bowel cancer or pre-cancerous polyps.
Key points to remember
Markers Are Not Diagnostic
A positive tumour marker result does not mean you have cancer. Similarly, a negative result does not guarantee you are cancer-free. Results must be interpreted by healthcare professionals alongside other tests.
Monitoring Over Time
Tumour markers are often most useful when tracked over time. Changes in marker levels (rising or falling) can provide important information about disease progression or treatment response.
False Positives & Negatives
Many factors can affect tumour marker levels, including benign conditions, medications, and laboratory variations. This is why clinical context is essential for accurate interpretation.
Consult Healthcare Professionals
Always discuss your results with a qualified healthcare professional who can consider your complete medical history, symptoms, and other test results to provide appropriate guidance.
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For official NHS guidance on cancer screening programmes:
Visit NHS Cancer Screening Information