Tumor Markers (General Concept)
Definition
Substances produced by cancer cells, or by normal cells in response to cancer. They are measured in blood, urine, or a tissue sample.
Tumor markers in the AdaGen menu and their associated cancers:
| Marker | Associated cancers | Main use |
|---|---|---|
| AFP (Alpha-fetoprotein) | Liver, ovary, testis | Liver cancer diagnosis, staging, treatment monitoring, prognosis |
| CEA (Carcinoembryonic antigen) | Colorectal, lung, stomach, thyroid, pancreas, breast, ovary | Treatment response, detecting recurrence after treatment |
| CA 15-3 | Breast cancer | Treatment monitoring in advanced-stage breast cancer |
| CA 125 | Ovarian cancer | Treatment effectiveness, detecting recurrence after completion |
| PSA (Prostate-specific antigen) | Prostate cancer | Screening, aiding diagnosis, treatment monitoring, detecting recurrence |
Purpose
To monitor whether cancer treatment is working and to detect recurrence after treatment.
Results
Values that fall during treatment suggest the treatment is working; values that rise after treatment may suggest recurrence.
Normal Values
Marker-specific and laboratory-specific.
Risks and Limitations
This is the limitation that most needs to be clearly stated in the glossary:
Tumor marker tests used for cancer screening cannot diagnose cancer on their own; a biopsy is required for a definitive diagnosis.
Errors are possible in both directions:
- False positive: Non-cancerous conditions can also raise markers; it may not be possible to distinguish cancer from other causes
- False negative: In some cancer patients, the marker associated with their specific cancer type does not rise