Tumour Markers: Cancer Screening & Monitoring Blood Tests
Tumour markers are proteins or other substances produced by cancer cells — or by normal cells in response to cancer — that can be measured in the blood. While they play a vital role in monitoring cancer treatment and detecting recurrence, it is essential to understand that tumour markers alone cannot diagnose cancer. They are one piece of the clinical puzzle, used alongside imaging, biopsy, and physical examination to guide medical decisions. Many benign conditions can elevate these markers, and some cancers produce no markers at all.
What Tumour Markers Can and Cannot Do
Understanding the limitations of tumour markers is just as important as understanding their value. Misinterpreting results can cause unnecessary anxiety or false reassurance.
What They CAN Do
Monitor treatment response — falling levels suggest therapy is working
Detect cancer recurrence early after initial treatment
Assess prognosis and tumour burden at diagnosis
Guide treatment decisions (e.g., switching chemotherapy regimens)
Screen high-risk populations (e.g., AFP for hepatitis B carriers)
What They CANNOT Do
Diagnose cancer on their own — a biopsy is always required for definitive diagnosis
Replace imaging (CT, MRI, PET) for detecting tumour location or spread
Reliably screen the general population for most cancers
Distinguish benign from malignant conditions with certainty
Detect all cancers — many cancers produce no measurable markers at all
Tumour Marker Reference Ranges
Reference ranges may vary between laboratories depending on the assay used. The values below are based on RCPA guidelines and commonly used assays in Australian pathology labs. Always compare your results with the reference range printed on your laboratory report.
| Marker | Normal Range | Unit | Notes |
|---|---|---|---|
Prostate-Specific Antigen (PSA) | < 4.0 (age-adjusted: <2.5 for 40–49, <3.5 for 50–59, <4.5 for 60–69, <6.5 for 70+) | µg/L | Prostate-specific but not cancer-specific. BPH, prostatitis, and cycling can all elevate PSA. |
Free PSA Ratio (Free/Total PSA) | > 25% | % | A lower free-to-total ratio (under 10–15%) increases the probability of prostate cancer. |
Carcinoembryonic Antigen (CEA) | < 3.0 (non-smokers) / < 5.0 (smokers) | µg/L | Most useful for monitoring colorectal cancer treatment. Not reliable for screening. |
Cancer Antigen 125 (CA-125) | < 35 | U/mL | Primarily used to monitor ovarian cancer. Endometriosis, fibroids, and pregnancy also raise levels. |
Carbohydrate Antigen 19-9 (CA 19-9) | < 37 | U/mL | Associated with pancreatic cancer. Also elevated in pancreatitis and bile duct obstruction. |
Alpha-Fetoprotein (AFP) | < 10 | µg/L | Elevated in hepatocellular carcinoma and testicular germ cell tumours. Also raised in cirrhosis and pregnancy. |
Cancer Antigen 15-3 (CA 15-3) | < 30 | U/mL | Used to monitor breast cancer treatment response. Not reliable for early detection. |
Beta-Human Chorionic Gonadotropin (β-hCG) | < 5 (non-pregnant) | IU/L | Elevated in testicular germ cell tumours and gestational trophoblastic disease. |
Lactate Dehydrogenase (LDH) | 120–250 | U/L | Non-specific marker elevated in many cancers, particularly lymphoma, leukaemia, and germ cell tumours. |
Which Markers for Which Cancers
Each tumour marker has specific cancer associations, but almost every marker can also be elevated by benign (non-cancerous) conditions. This is why a single elevated result should never be interpreted in isolation.
PSA
Prostate cancer
Benign prostatic hyperplasia (BPH), prostatitis, urinary tract infection, vigorous exercise, cycling, recent ejaculation
CEA
Colorectal, lung, breast, pancreatic, gastric
Smoking, inflammatory bowel disease, cirrhosis, peptic ulcer, hypothyroidism
CA-125
Ovarian (epithelial), endometrial, fallopian tube
Endometriosis, fibroids, pelvic inflammatory disease, pregnancy, peritonitis, menstruation
CA 19-9
Pancreatic, biliary (cholangiocarcinoma), gastric
Pancreatitis, bile duct obstruction, cholangitis, cirrhosis
AFP
Hepatocellular carcinoma, testicular germ cell tumours
Cirrhosis, chronic hepatitis B/C, pregnancy (normal elevation)
CA 15-3
Breast cancer (metastatic monitoring)
Liver disease, benign breast conditions, ovarian cysts
β-hCG
Testicular germ cell tumours, gestational trophoblastic disease
Pregnancy, hypogonadism, cannabis use (rarely)
PSA: The Prostate Screening Debate
PSA is the most widely discussed tumour marker in Australia, and one of the most controversial. The Royal Australian College of General Practitioners (RACGP) does not recommend routine PSA screening for the general population because of the high rate of false positives and the risk of overdiagnosis — detecting slow-growing cancers that would never cause symptoms or death in a patient's lifetime.
Australian Guidelines (RACGP)
Not recommended as routine population screening
Informed decision-making advised for men aged 50–69
High-risk men (family history, BRCA2 carriers) may consider testing from age 40
Discuss benefits AND harms with your GP before testing
If PSA is elevated, repeat before proceeding to biopsy
Advanced PSA Metrics
PSA density: PSA divided by prostate volume (MRI). Higher density = higher risk
PSA velocity: Rate of change over time. A rise > 0.75 µg/L per year raises suspicion
Free-to-total ratio: Free PSA < 10% = higher cancer risk; > 25% = more likely benign
Age-adjusted ranges: Upper limits increase with age (prostate grows naturally)
PHI (Prostate Health Index): Combines total, free, and p2PSA for better specificity
Understanding Elevated Results
An elevated tumour marker does not necessarily mean cancer. Equally, a normal result does not guarantee you are cancer-free. Here is how oncologists interpret tumour marker results:
Most commonly caused by benign conditions. Your doctor will usually recommend repeating the test in 4–6 weeks to see if the level returns to normal or continues to rise.
Warrants further investigation with imaging (CT, ultrasound, or MRI). Could still be benign, particularly in the context of known conditions like cirrhosis or endometriosis.
Strongly suggestive of malignancy, though not diagnostic. Will typically prompt urgent imaging, specialist referral, and potentially biopsy.
The trend is often more informative than any single value. A steadily rising marker, even within the normal range, may indicate early recurrence and warrants close monitoring.
Who Should Have Tumour Marker Testing?
Tumour marker testing is not recommended as routine screening for the general population. Most tumour markers lack the specificity needed for population-wide screening and produce unacceptably high rates of false positives. Testing is indicated in specific clinical scenarios:
Appropriate Indications
Monitoring known cancer during and after treatment
Detecting recurrence after curative surgery or therapy
Investigating suspicious symptoms with other findings (e.g., imaging)
High-risk populations (e.g., AFP for chronic hepatitis B carriers)
Family history of BRCA-related cancers (PSA, CA-125 in selected cases)
Staging and prognosis assessment at diagnosis
Not Appropriate For
Routine health check-ups in asymptomatic people
General "cancer screening" without clinical indication
Self-ordered testing without medical supervision
Reassurance testing in anxious but low-risk individuals
As a substitute for recommended screening (e.g., bowel cancer FOBT)
Standalone diagnosis without imaging or biopsy confirmation
Related Blood Test Guides
When to See Your Doctor
These symptoms have many possible causes, most of which are not cancer. However, early detection significantly improves outcomes for those cancers that are present, so prompt investigation is always worthwhile.
Track Your Tumour Markers Over Time
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Get Started FreeMedical Disclaimer: This guide is for educational purposes only and does not constitute medical advice. Tumour marker results must always be interpreted by a qualified healthcare professional in the context of your symptoms, medical history, imaging, and other test results. Cancer diagnosis requires specialist assessment including biopsy confirmation. Never use tumour marker results alone to make decisions about your health.