Tumor Markers – Understanding Cancer Biomarkers
Tumor markers, also known as cancer biomarkers, are molecules that provide valuable clues about the presence and behavior of cancer. They can be found in the blood, urine, or tissues of patients, and are produced either directly by tumor cells or by the body as a response to cancer.
What Are Tumor Markers?
Definition
Tumor markers are biological substances measurable in fluids or tissues that provide information about the presence, growth, or recurrence of cancer. They are not always specific to a single cancer but can still indicate abnormal cell activity.
Types of Tumor Markers
- Proteins – PSA, CEA, CA 125
- Enzymes – LDH (lactate dehydrogenase), NSE (neuron-specific enolase)
- Hormones – hCG in testicular cancer
- Glycoproteins – CA 19-9 in pancreatic cancer
- Genetic markers – Mutations such as KRAS, BCR-ABL
- Circulating tumor DNA (ctDNA) – Fragments of cancer DNA in blood, a key tool in liquid biopsy
List of Common Tumor Markers
Major Tumor Markers
| Tumor Marker | Associated Cancer | Clinical Use |
|---|---|---|
| PSA (Prostate-Specific Antigen) | Prostate cancer | Screening, monitoring |
| CA 125 | Ovarian cancer | Monitoring, recurrence |
| AFP (Alpha-fetoprotein) | Liver, germ cell tumors | Diagnosis, prognosis |
| CEA (Carcinoembryonic antigen) | Colorectal, pancreatic, breast | Post-surgery monitoring |
| HER2 | Breast, gastric cancer | Targeted therapy decision |
| CA 19-9 | Pancreatic, biliary cancer | Disease progression |
| hCG (Human chorionic gonadotropin) | Testicular cancer, trophoblastic disease | Diagnosis, monitoring |
| BCR-ABL | Chronic myeloid leukemia (CML) | Genetic diagnosis |
| NSE (Neuron-specific enolase) | Small cell lung cancer | Monitoring treatment |
| LDH (Lactate dehydrogenase) | Lymphomas, testicular cancer | Prognosis |
Clinical Applications of Tumor Markers
Early Detection & Screening
Example: PSA is widely used in prostate cancer screening, though controversial due to overdiagnosis.
Diagnosis & Classification
Markers like AFP and hCG help distinguish between germ cell tumor types.
Treatment Monitoring
Falling tumor marker levels indicate therapy effectiveness.
Example: CA 125 is monitored during ovarian cancer chemotherapy.
Recurrence Detection
CEA levels rising post-surgery may signal colorectal cancer recurrence.
Precision Medicine
HER2, KRAS, and EGFR mutations are predictive biomarkers guiding targeted therapies and immunotherapy.
Laboratory Testing Methods
Immunoassays & ELISA
Most protein-based tumor markers (PSA, CEA, CA 125) are detected with immunoassays.
PCR & Genetic Testing
Essential for detecting mutations like BCR-ABL, KRAS, EGFR.
Immunohistochemistry (IHC)
Used in tissue samples to detect HER2, ER/PR, and Ki-67.
Liquid Biopsy
A revolutionary approach analyzing circulating tumor DNA (ctDNA) in blood, enabling non-invasive cancer detection and monitoring.