Tumour Markers — Cancer Detection and Monitoring

Important caveat:: Elevated tumour markers do NOT confirm cancer. Many non-cancerous conditions (infection, inflammation, benign tumours, pregnancy) elevate these markers. Conversely, early-stage cancers may produce no detectable marker elevation.

Tumour markers are most valuable for:

• **Monitoring known cancer** during and after treatment

• **Detecting recurrence** after apparent cure

• **Assessing prognosis** at diagnosis

• **Selective screening** in high-risk populations (e.g., PSA in men over 50)

PSA (Prostate-Specific Antigen):: Produced by prostate cells. Elevated in prostate cancer, but also in BPH and prostatitis. The most widely used cancer screening marker for men. Serial PSA testing (watching for rising trend) is often more informative than a single value.

CEA (Carcinoembryonic Antigen):: Elevated in colorectal, lung, breast, gastric, and pancreatic cancers. Smokers have slightly elevated baseline CEA. Primarily used to monitor colorectal cancer treatment and detect recurrence.

CA-125:: Mainly associated with ovarian cancer. Elevated in ~80% of advanced ovarian cancers. Also rises in endometriosis, fibroids, pancreatitis, and even menstruation — limiting its specificity as a screener. Best used alongside pelvic ultrasound in high-risk women.

AFP (Alpha-Fetoprotein):: Elevated in hepatocellular carcinoma (liver cancer) and testicular germ cell tumours. Also elevated in normal pregnancy and liver cirrhosis. Standard surveillance test every 6 months for cirrhosis patients.

CA 19-9:: Most elevated in pancreatic cancer. Also elevated in cholangiocarcinoma (bile duct cancer) and GI cancers. Limited use as a screener but valuable for monitoring pancreatic cancer treatment.

CA 15-3 / CA 27.29:: Associated with breast cancer — used to monitor treatment and detect recurrence, not for initial diagnosis.

Beta-hCG (Serum):: Primarily elevated in pregnancy. In non-pregnant individuals, very high levels indicate choriocarcinoma or testicular cancer.

Appropriate uses::

• **Known cancer diagnosis:** Track response to chemotherapy, radiation, or surgery — markers should fall with effective treatment

• **Post-treatment surveillance:** Rising markers after successful treatment may be the earliest sign of recurrence, often months before imaging shows a tumour

• **High-risk individuals:** PSA for men over 50 (or 45 with family history); AFP surveillance in cirrhosis patients; CA-125 for women with BRCA1/2 mutations

Serial testing matters more than single values.: A rising trend over time is more meaningful than a single slightly elevated result.

• **Men over 50:** PSA baseline, and annually thereafter (or from 45 with family history of prostate cancer)

• **Anyone with chronic liver disease or cirrhosis:** AFP every 6 months for hepatocellular carcinoma surveillance

• **Women with BRCA1/2 mutations or strong family history of ovarian cancer:** CA-125 + pelvic ultrasound

• **Known cancer patients:** As directed by oncologist for monitoring

• **Heavy smokers:** CEA can serve as one input in a lung health assessment alongside imaging