Defining tumours and tumour marker tests
A tumour is a solid mass of tissue that develops due to abnormal cell division and growth. They are also known as neoplasms and are generally classified into two categories: benign (non-cancerous) and malignant tumours (cancerous). Benign tumours usually do not cause problems as they stay confined in their primary location without invading any other part of the body. However, if the tumour compresses a vital structure or organ, it can become problematic, requiring prompt management. Conversely, malignant tumours have the potential to spread locally or to distant sites (metastasis) through the bloodstream or lymphatic system. If they continue to grow and spread, they can pose a considerable threat to one’s life.
Tumour markers play an important role in determining the prognosis as they can provide essential information about the type of cancer. While tumour marker tests are not carried out to diagnose or rule out cancer, they are beneficial in demonstrating how aggressive the tumour is and monitoring the treatment response.
Understanding tumour marker tests: Purpose and benefits
Tumour markers are usually found abundantly in the tissues, blood or urine of patients with cancer. Most of these substances are proteins, and they are normally produced by the tumour itself. However, these cancer markers can also be made by healthy cells in response to the presence of the tumour. Tumour marker tests are used to determine whether or not you have these substances and to assess their quantity. Although Gastroenterologists use these tests as supplementary tools in detecting cancer, they cannot be used as a diagnostic test. In addition, several other medical conditions can cause high levels of tumour markers.
Benefits of tumour marker tests
- Aids with early detection of cancer
- Helps with cancer staging
- Serves as a guide for imaging studies
- Assists with treatment monitoring
- Evaluates the treatment response
- Enhances the treatment outcome
- Assesses cancer recurrence
- Reduces the need for invasive tests
- Helps with cancer research and trials
Digestive tumour markers: Exploring common tumour marker tests and their techniques
According to a study conducted on the ‘Global Burden of 5 Major Types of Gastrointestinal Cancer’, there were over 3 million gastrointestinal cancer-related deaths worldwide, with around 4 million new gastrointestinal cancers in 2018. As per the findings of this study, although the prevalence of gastrointestinal cancers has decreased, certain malignancies will have an immense impact on public health. Another study conducted on the use of tumour markers in gastrointestinal cancers revealed that tumour markers have a significant role in the postoperative surveillance of these cancers. However, further trials are yet to be carried out to evaluate their function as a general screening tool and to assess their true value in clinical practice.
Digestive tumour markers are associated with cancers of the digestive system, such as colorectal cancer, gastrointestinal cancer, oesophageal cancer, stomach cancer, and pancreatic cancer. Just as any other cancer marker, digestive tumour markers are used to help detect gastrointestinal cancers, monitor the treatment progress, and assess recurrence risk.
When it comes to gastrointestinal malignancies, three digestive tumour markers are commonly used in a range of general health screening tests:
- Carcinoembryonic Antigen (CEA)
- Alpha-Fetoprotein (AFP)
- Carbohydrate Antigen 19-9 (CA19-9).
The CEA tumour marker test assesses the levels of CEA protein, and a high level may hint towards a cancer diagnosis. However, it is important to note that patients can have normal CEA levels despite having gastrointestinal cancer. While CEA is the most commonly used tumour marker for colorectal cancer screening, those with bowel cancers may have high levels of CEA in their blood. Those suffering from conditions like hepatitis, cirrhosis, pancreatitis, and inflammatory bowel disease (IBD) may also notice an increase in their CEA levels. Furthermore, smoking can contribute to the elevation of this protein; therefore, patients will be advised to stop smoking before they do this test. CEA levels are usually analysed by taking blood samples, but in some cases, they might be tested by obtaining samples of other bodily fluids.
AFP, on the other hand, may indicate the presence of certain liver cancers such as hepatocellular carcinoma (HCC) and germ cell tumours. However, as with CEA, the tumour marker isn’t specific to liver cancer and may be increased by other malignancies, including breast and lung cancer. AFP may also be found in those with colorectal cancer, and this tumour marker is most frequently used to monitor the treatment progress of individuals with HCC. No specific preparation is required to perform the AFP tumour marker test, and it usually takes around five minutes to get the blood sample. Once the sample is obtained, it will be sent for analysis.
While CA19-9 levels can rise due to different types of cancers and various other medical conditions, it is commonly used to screen for pancreatic cancer. As with CEA and AFP, this tumour marker test is beneficial in monitoring the progress of the cancer, tracking the treatment response, and determining the risk of recurrence. Other gastrointestinal cancers that can increase the levels of this protein are gastric, bile duct, and colorectal cancers. While you will not need any preparations for this tumour marker blood test, certain vitamins might have to be avoided prior to the test.
Factors influencing tumour marker levels: Limitations and considerations of tumour marker tests
Tumour marker tests are generally performed in conjunction with a detailed history-taking, physical examination and various other diagnostic investigations. If the tests show abnormal results, further investigation will be required. While the tumour marker test is an important supplementary tool, it isn’t free from limitations.
Listed below are some of the key limitations:
- Some cancers do not have any known tumour markers, and some patients may not present with high tumour marker levels, even if they have a type of cancer that usually produces tumour markers.
- The tumour marker levels may not rise until the disease worsens or recurs, and those without cancer may show high tumour marker levels. Some tumour markers are not specific and may be elevated due to different types of cancers or conditions.
- In some instances, tumour marker tests may give a ‘false positive’ or ‘false negative’ result. A false positive implies the patient has cancer, although they are healthy, and a false negative will indicate that the patient does not have cancer when they actually do.
When combined with other diagnostic tests, tumour marker tests can be useful in gauging a patient's prognosis and monitoring the treatment progress. Although tumour marker tests do have certain limitations, they can provide a lot of information about a cancer and reduce the need for more invasive tests.
Frequently Asked Questions
Are tumour marker tests accurate?
The accuracy will depend on the type of cancer and tumour marker assessed. While some may have a high specificity and sensitivity, tumour marker tests cannot provide 100% accuracy. However, they can be of great value when combined with other diagnostic investigations.
Does a high tumour marker level denote cancer?
No, not necessarily. While an elevated level of tumour markers may imply the patient has cancer, it cannot be used as a stand-alone test to confirm the diagnosis.
What causes tumour markers to rise?
Several conditions, including cancer, can cause the circulating levels of tumour markers to rise. Here are some of the non-cancerous gastrointestinal conditions that can cause high tumour marker levels:
What are the three most common tumour markers?
In the realm of gastroenterology, Carcinoembryonic Antigen (CEA), Alpha Fetoprotein (AFP) and Carbohydrate Antigen 19-9 (CA19-9) are the most commonly used digestive tumour markers.
Visit Alpha Digestive & Liver Centre
For more information on digestive tumour marker tests and their benefits, get in touch with us at Alpha Digestive & Liver Centre and book an appointment with our experienced Gastroenterologist, Dr Benjamin Yip. You may also browse through our blog posts featuring educational information about various gastrointestinal subject matters, including ‘How Does Alcohol Affect the Liver’, ‘Capsule Endoscopy Vs Conventional Endoscopy’, and many other essential content.
- National Library of Medicine. “Global Burden of 5 Major Types Of Gastrointestinal Cancer”, Published online 2 April 2020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8630546/#:~:text=With%20an%20estimated%204.8%20million,related%20deaths%20(Figure%201)
- National Library of Medicine. “Use of Tumor Markers in Gastrointestinal Cancers: Surgeon Perceptions and Cost-Benefit Trade-Off Analysis”, Published online 22 December 2020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5374165/
- Cancer.Net. “Tumour Marker Tests”, Accessed November 26, 2023. https://www.cancer.net/navigating-cancer-care/diagnosing-cancer/tests-and-procedures/tumor-marker-tests
- Cleveland Clinic. “Tumour Markers”, Accessed November 27, 2023. https://my.clevelandclinic.org/health/diagnostics/24813-tumor-markers
- Canadian Cancer Society. “Tumour Markers”, Accessed November 27, 2023. https://cancer.ca/en/treatments/tests-and-procedures/tumour-markers
- Medline Plus. “CEA Test”, Accessed November 28, 2023. https://medlineplus.gov/lab-tests/cea-test/
- Medline Plus. “Alpha Fetoprotein Test”, Accessed November 28, 2023. https://medlineplus.gov/lab-tests/alpha-fetoprotein-afp-test/
- Medline Plus. “CA 19-9 Blood Test (Pancreatic Cancer)”, Accessed November 28, 2023. https://medlineplus.gov/lab-tests/ca-19-9-blood-test-pancreatic-cancer/