What Do Tumor Markers Mean?

## What Are Tumor Markers? Tumor markers are substances — usually proteins — that are produced by cancer cells or by normal cells in response to cancer, and can be measured in blood, urine, or tissue. They are used to: - Monitor response to treatment - Detect recurrence after treatment - In some cases, help diagnose cancer (though rarely alone) - Provide prognostic information ## Common Tumor Markers by Cancer Type ### CEA (Carcinoembryonic Antigen) - **Primary use:** Colorectal cancer monitoring - Also elevated in: lung, pancreatic, gastric, breast cancer - Normal: < 2.5–5 ng/mL (varies by lab, smoking status) - **Not diagnostic** — elevated CEA alone does not confirm cancer ### PSA (Prostate-Specific Antigen) - **Primary use:** Prostate cancer screening and monitoring - Rising PSA after treatment can indicate recurrence - Also elevated in: benign prostatic hyperplasia (BPH), prostatitis ### CA-125 - **Primary use:** Ovarian cancer monitoring - High sensitivity for serous ovarian cancer recurrence - Also elevated in: endometriosis, fibroids, liver disease, pregnancy - Not reliable as a standalone screening test ### CA 19-9 - **Primary use:** Pancreatic cancer, biliary cancer monitoring - Also elevated in: pancreatitis, cholangitis - Not produced in patients who are Lewis antigen-negative (~10% of people) ### AFP (Alpha-Fetoprotein) - **Primary use:** Hepatocellular carcinoma (liver cancer), germ cell tumors - Major diagnostic and monitoring role in liver cancer ### Beta-hCG (Human Chorionic Gonadotropin) - **Primary use:** Testicular cancer (non-seminoma), gestational trophoblastic disease - Highly sensitive marker for these cancers ### LDH (Lactate Dehydrogenase) - **Primary use:** Lymphoma, leukemia, testicular cancer, melanoma - Non-specific — elevated in many conditions - Primarily a prognostic marker (higher LDH = more disease burden) ## Important Limitations **Tumor markers are not diagnostic tests.** An elevated tumor marker does not confirm cancer, and a normal tumor marker does not rule it out. - Many cancers don't produce markers - Many conditions other than cancer can elevate markers - Some people's cancers never produce a given marker **Use tumor markers in context.** A rising CEA after colorectal cancer surgery is concerning for recurrence and warrants further evaluation — but a single elevated CEA alone doesn't tell the whole story. ## Practical Tips - Know your baseline values (established before or at the start of treatment) - Track values over time — the trend matters more than any single number - Ask your oncologist which markers are relevant for your cancer and what changes would warrant investigation