Tumor Markers: PSA, CA-125, and AFP Explained
Tumor markers are substances—often proteins—produced by cancer cells or by the body in response to cancer. These markers are typically found in the blood, urine, or tissues and are used in cancer screening, diagnosis, and treatment monitoring. While not all cancers produce detectable markers, and not all markers indicate cancer, they play a crucial role in modern oncology.
What Are Tumor Marker Tests?
Tumor marker tests measure specific biomolecules that can be elevated in certain types of cancer. Here, we focus on three widely used markers:
1. PSA (Prostate-Specific Antigen)
Purpose:
The PSA test measures the level of prostate-specific antigen in the blood. PSA is a protein produced by the prostate gland. Elevated levels may suggest prostate cancer, benign prostatic hyperplasia (BPH), or prostatitis.
Normal Range: Usually less than 4.0 ng/mL, but values can vary based on age and lab.
Clinical Use: Screening men for prostate cancer, monitoring disease progression, and evaluating treatment response.
📚 Trusted Source:
American Cancer Society – PSA Test
2. CA-125 (Cancer Antigen 125)
Purpose:
CA-125 is a protein found on the surface of many ovarian cancer cells. The test measures its level in the blood.
Used Primarily For:
Detecting ovarian cancer, particularly in women with a family history or symptoms.
Monitoring cancer recurrence or treatment response.
Limitations: CA-125 can also be elevated in non-cancerous conditions such as endometriosis, menstruation, or pelvic inflammatory disease, making it unsuitable as a stand-alone screening tool.
Normal Range: Below 35 U/mL.
📚 Trusted Source:
Mayo Clinic – CA-125 Test
3. AFP (Alpha-Fetoprotein)
Purpose:
AFP is a protein normally produced by the liver and yolk sac of a developing fetus. In adults, elevated levels can signal:
Liver cancer (hepatocellular carcinoma)
Germ cell tumors (especially testicular cancer)
Metastatic liver disease
Normal Range: Less than 10 ng/mL in adults.
AFP testing is commonly combined with imaging to increase diagnostic accuracy.
📚 Trusted Source:
MedlinePlus – AFP Tumor Marker
Importance and Limitations of Tumor Markers
While tumor markers provide valuable insights, they are not definitive diagnostic tools. Elevated levels may occur in benign conditions, and normal results don’t always rule out cancer. For this reason, tumor marker tests are usually used alongside imaging, biopsies, and other clinical assessments.
Conclusion
Tumor markers like PSA, CA-125, and AFP serve essential roles in cancer screening, diagnosis, monitoring treatment response, and checking for recurrence. However, their use should always be interpreted by medical professionals within the context of a broader diagnostic plan.
Incorporating tumor marker testing into routine care for high-risk individuals can lead to earlier detection and more effective treatment outcomes.
Let me know if you’d like a version with a comparison table, downloadable patient handout, or more tumor markers like CEA and CA 19-9.