Unit Converter
CA 72-4 (Cancer antigen 72-4)
(TAG-72 Glycoprotein – Tumor Marker for Gastric & Ovarian Cancer)
Synonyms
- CA 72-4
- Cancer Antigen 72-4
- TAG-72 (Tumor-associated glycoprotein-72)
- ST-439 antigen
- Mucin-like glycoprotein
- Gastrointestinal tumor marker
Units of Measurement
- U/mL (Units per milliliter - standard)
- kU/L (kilo-units per liter)
1 U/mL = 1 kU/L
Description
CA 72-4 is a high–molecular-weight mucin-like glycoprotein known as TAG-72, expressed on mucin-producing epithelial tumors.
Primary clinical use:
- Gastric cancer diagnosis & monitoring
- Ovarian mucinous carcinoma monitoring
It is not a general cancer screening test.
CA 72-4 is less commonly used than CA 19-9 or CEA but adds value in gastric cancer, especially when combined with other markers.
Physiological Source
Normally present at low levels on:
- Gastrointestinal epithelium
- Respiratory epithelium
- Reproductive tract mucosa
Tumors overexpress TAG-72 and shed it into the bloodstream.
Clinical Significance
Elevated CA 72-4
1. Gastric Cancer (Primary Use)
- Highest sensitivity among tumor markers for gastric cancer
- Often elevated in advanced or recurrent disease
- Serial monitoring used for:
- Treatment response
- Disease progression
- Recurrence detection
- Treatment response
2. Ovarian Mucinous Carcinoma
Better marker than CA-125 for mucinous subtype.
3. Colorectal Cancer
Moderate elevations in:
- Mucinous adenocarcinomas
- Advanced GI tumors
4. Other Malignancies
Possible increases in:
- Pancreatic cancer
- Lung cancer
- Breast cancer
5. Benign Conditions
Usually mild elevation only:
- Gastritis
- Peptic ulcer disease
- Liver cirrhosis
- Pulmonary fibrosis
Benign elevations rarely exceed 10–20 U/mL.
Low or Normal CA 72-4
Normal; does not exclude cancer.
Some cancers do not secrete TAG-72.
Reference Intervals
(Tietz 8E + ESMO + NCCN + Mayo + ARUP)
Normal Range
- < 6 U/mL
(Varies slightly by manufacturer; some use <4 or <7 U/mL)
Interpretation
- 6–10 U/mL → mild elevation (often benign)
- >10–20 U/mL → suspicious; correlate with imaging
- >20 U/mL → suggests malignancy (especially gastric)
- >100 U/mL → very concerning for advanced disease
Monitoring
- Decreasing → response to treatment
- Rising → recurrence or progression
Unit Meanings
| Unit | Meaning |
| U/mL | Units per milliliter |
| kU/L | kilo-units per liter |
Diagnostic Uses
1. Gastric Cancer
- Best tumor marker for gastric adenocarcinoma
- Used for:
- Baseline evaluation
- Monitoring therapy
- Detecting recurrence
- Baseline evaluation
2. Ovarian Mucinous Tumors
- Helpful when CA-125 is normal
- Supports diagnosis and follow-up
3. Colorectal Cancer
- Adjunct tumor marker
- Useful when CEA and CA 19-9 are inconclusive
4. Combined Marker Panels
Improved sensitivity when CA 72-4 is paired with:
- CEA
- CA 19-9
- CA 125 (in ovarian mucinous cancers)
Analytical Notes
- Measured by immunoassay
- Hemolysis minimally affects results
- Avoid interpretation during severe inflammation
- Serial measurements should use the same platform
- Turnaround time: typically 1 day
Clinical Pearls
- CA 72-4 is more specific for gastric cancer than CA 19-9.
- Not useful for screening because of low sensitivity in early disease.
- Combined with CEA and CA 19-9, it improves diagnostic accuracy.
- Elevated CA 72-4 in ovarian cancer suggests mucinous subtype, not serous.
- Benign diseases rarely exceed 15–20 U/mL.
Interesting Fact
TAG-72, the source antigen of CA 72-4, is being explored as a target for monoclonal antibody imaging and therapy in GI cancers.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Tumor Markers.
- ESMO Clinical Practice Guidelines - Gastric Cancer.
- NCCN Guidelines - Gastric & Ovarian Cancer.
- IFCC - Tumor Marker Harmonization.
- Mayo Clinic Laboratories - CA 72-4.
- ARUP Consult - Gastrointestinal Tumor Markers.
- MedlinePlus / NIH - Tumor Marker Overview.