Cancer 1 Section4 Lessons10 Weeks
Tumor Markers & Their Siginificance
Definition
- Tumor markers are biochemical substances produced by tumor cells or host tissues in response to tumor presence.
- They are detectable in blood, urine, or tissues.
- Used as aids in cancer diagnosis, prognosis, and monitoring — not for definitive diagnosis alone.
Ideal Characteristics of a Tumor Marker
- High sensitivity and specificity,
- Correlates with tumor burden,
- Rises with recurrence and falls with treatment,
- Should help in screening, diagnosis, prognosis, and monitoring therapy.
Types of Tumor Markers
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A. Oncofetal Antigens
Marker | Normal Source | Associated Tumor |
AFP (Alpha-fetoprotein) | Fetal yolk sac, liver | Hepatocellular carcinoma, Germ cell tumors (yolk sac type) |
CEA (Carcinoembryonic antigen) | Fetal gut | Colorectal carcinoma, gastric, pancreatic, breast cancers |
B. Enzymes
Marker | Tumor Association |
PSA (Prostate-specific antigen) | Prostate carcinoma, benign prostatic hypertrophy |
ALP (Alkaline phosphatase) | Bone metastases, hepatobiliary cancers |
Neuron-specific enolase (NSE) | Small cell lung carcinoma, neuroblastoma |
C. Hormones
Marker | Tumor Association |
β-hCG | Choriocarcinoma, germ cell tumors |
Calcitonin | Medullary carcinoma of thyroid |
ACTH / ADH (ectopic production) | Small cell carcinoma of lung |
D. Cell surface antigens
Marker | Tumor Association |
CA-125 | Ovarian carcinoma (epithelial type) |
CA 15-3 / CA 27-29 | Breast carcinoma |
CA 19-9 | Pancreatic and biliary tract carcinoma |
E. Genetic/Molecular markers
Marker | Tumor Association |
HER2/neu (ERBB2) | Breast carcinoma – targeted by Trastuzumab |
BCR-ABL fusion gene | Chronic Myeloid Leukemia (Philadelphia chromosome) |
KRAS, EGFR mutations | Lung, colon cancers – targetable mutations |
BRCA1/2 | Hereditary breast and ovarian cancers |
Clinical significance
Use | Example |
Screening (limited use) | PSA (prostate), AFP (HCC in high-risk) |
Diagnosis / Differential diagnosis | β-hCG for germ cell tumors vs. others |
Prognosis | HER2/neu, CEA levels |
Monitoring therapy | PSA post-prostatectomy, CEA after colon surgery |
Detection of recurrence | Rising CEA or CA-125 indicates relapse |
Limitations
- Lack of specificity: can be elevated in benign diseases.
- Lack of sensitivity: may be normal in early-stage cancer.
- Must be interpreted with clinical and radiologic findings.
- Best used for monitoring, not screening (except few cases).
Summary
Marker | Major Use | Associated Tumor |
AFP | Diagnosis & monitoring | HCC, yolk sac tumor |
CEA | Monitoring | Colorectal, pancreatic, breast |
PSA | Screening & monitoring | Prostate cancer |
β-hCG | Diagnosis | Choriocarcinoma, germ cell tumors |
CA-125 | Monitoring | Ovarian carcinoma |
CA 19-9 | Monitoring | Pancreatic cancer |
HER2/neu | Prognostic / Targeted therapy | Breast cancer |