Are Tumour Markers Reliable in Health Screening?

In recent years, tumour marker tests have gained attention as part of comprehensive health screening programs. Many people wonder whether these blood tests can reliably detect cancer early and provide peace of mind about their health. While tumour markers can play an important role in cancer management, their reliability in general health screening is more complex than many people expect.

What Are Tumour Markers?
Tumour markers are substances (often proteins) found in the blood, urine, or body tissues that may be produced by cancer cells or by the body in response to cancer. Doctors can measure these markers through laboratory tests to help identify certain types of cancer or monitor how a patient responds to treatment.

Some commonly tested tumour markers include:

• PSA (Prostate-Specific Antigen) – associated with prostate conditions and prostate cancer
• CA-125 – linked to ovarian cancer
• CEA (Carcinoembryonic Antigen) – associated with colorectal and other cancers
• AFP (Alpha-fetoprotein) – related to liver cancer and some germ cell tumors
• CA 19-9 – sometimes associated with pancreatic cancer

Although these markers may rise in people with cancer, they are not exclusively produced by cancer cells.

Why Tumour Markers Are Used In Medicine?
Tumour markers are most valuable in monitoring cancer treatment and detecting recurrence rather than detecting cancer in healthy individuals. For example, if a patient previously diagnosed with cancer has decreasing tumour marker levels during treatment, it may indicate that therapy is working. Similarly, rising tumour marker levels after treatment could suggest that the cancer has returned, prompting further investigation.

Limitations of Tumour Markers In Health Screening
Despite their usefulness in certain clinical situations, tumour markers have significant limitations when used for general health screening.

1. False Positives
Tumour marker levels can increase due to non-cancerous conditions. For example:

• PSA may rise due to prostate enlargement or infection.
• CA-125 can increase during menstruation, pregnancy, or conditions like endometriosis.
• CEA levels may rise in smokers or people with inflammatory diseases.

These false positives may cause unnecessary anxiety and lead to additional tests or procedures.

2. False Negatives
Not all cancers produce detectable tumour markers. A person may have cancer even when tumour marker levels appear normal. This means relying solely on these tests could provide a false sense of security.

3. Lack of Specificity
Many tumour markers are not specific to one type of cancer. Elevated levels may be linked to multiple conditions, making it difficult to determine the exact cause without further diagnostic testing.

Alternatives and the Importance of National Guidelines
The limitations of tumour markers have prompted the development and recommendation of more established, evidence-based screening methods in the National Guidelines.

Established, Cancer-Specific Screening Methods:
These methods form the bedrock of national cancer control strategies and are recommended based on a patient's age, gender, and established risk factors. They target specific, high-prevalence cancers with interventions proven to reduce morbidity and mortality:

• For Colorectal Cancer: The Faecal Occult Blood Test (FOBT), specifically the Faecal Immunochemical Test (FIT), or colonoscopy serve as the gold standard. FIT is a non-invasive, accessible test that detects hidden blood in the stool, often an early sign of polyps or cancer. Colonoscopy, while more invasive, allows for direct visualisation of the entire colon and the immediate removal of pre-cancerous polyps, making it both a diagnostic and preventative procedure.
• For Breast Cancer: Mammography remains the cornerstone of screening. This low-dose X-ray examination can detect subtle abnormalities, such as masses or microcalcifications, often years before a lump can be felt, significantly improving the chances of successful treatment.
• For Cervical Cancer: The Pap smear (Papanicolaou test), which looks for precancerous and cancerous cell changes on the cervix, and Human Papillomavirus (HPV) DNA testing, which detects the high-risk virus strains that cause nearly all cervical cancers, are essential tools. Increasingly, national programmes are adopting primary HPV testing as it offers higher sensitivity for detecting disease risk.

The Landscape of Emerging Genomic Technologies:
The field of cancer detection is rapidly advancing, with exciting new technologies emerging that promise earlier, less invasive screening options. These methods primarily focus on identifying molecular signals of cancer circulating in the bloodstream:

• Circulating Tumour DNA (ctDNA) and Circulating Tumour RNA (ctRNA): Companies like SpotMAS and Lucence are pioneering this space with "liquid biopsy" technologies. These multi-cancer early screening tests look for fragments of DNA or RNA shed by tumour cells into the blood. The ability to detect these specific genetic signatures offers the potential for highly sensitive, multi-cancer early detection. These technologies hold immense promise for overcoming the limitations of single-marker tumour tests. If you would like to learn more about multi-cancer early screening before booking, view our multi-cancer early screening FAQ and educational guide.

It is crucial to understand that while these alternatives, particularly the emerging genomic tests, offer new possibilities, they do not replace established national screening guidelines. These guidelines are built upon decades of research to demonstrate effectiveness, safety, and cost-effectiveness in population-wide screening and should remain the primary strategy for early cancer detection.

When Tumour Markers May Be Helpful in Screening
Tumour marker testing can, in certain circumstances, be a valuable adjunct when integrated with other screening modalities and clinical assessment. For instance, annual Alpha-Fetoprotein (AFP) screening, combined with liver ultrasound, is advised for patients who are Hepatitis B or C carriers. Furthermore, Prostate-Specific Antigen (PSA) screening is recommended for men aged 50 and above, or earlier if there is a family history.

Other tumour markers, such as Carcinoembryonic Antigen (CEA), Cancer Antigen 125 (CA125), and Cancer Antigen 19.9 (CA19.9), are not routinely recommended. Nevertheless, patients with specific concerns may consult with our Minmed doctors regarding specific cancer screening options beyond those covered by the national screening programme during their general health examination.

Conclusion
Tumour markers can be valuable tools in modern medicine, particularly for monitoring cancer treatment and detecting recurrence. However, their reliability as standalone tests in general health screening is limited due to false positives, false negatives, and lack of specificity.

Therefore, during a health screening consultation at Minmed, our initial approach involves a comprehensive review of the patient's personal and family history, alongside any specific concerns they may have. This information guides the recommendation of a thorough screening package that incorporates tumour marker tests as a component of a broader, personalised health assessment, rather than relying upon them in isolation.