Tumor Markers: What They Show, When to Get Tested, and How to Understand Results

What are tumor markers and why are they needed?

Tumor markers (or cancer markers) are specific substances produced by cancer cells or normal cells of the body in response to the presence of a malignant tumor. They can be detected in blood, urine, tissues, or other biological fluids. Biomarkers in general are measurable indicators that can indicate the presence of a disease, its progression, or response to treatment. They are used in various fields of medicine, for example, to assess the state of the cardiovascular system [7], in intracranial hemorrhage [5], or for monitoring neurological diseases such as multiple sclerosis, where blood sample collection for analysis is important [4].

In oncology, tumor markers are not a universal screening method for early cancer diagnosis in healthy people. Their main purpose is:

• Monitoring treatment efficacy: A decrease in tumor marker levels after starting therapy may indicate a positive tumor response to treatment.
• Detecting recurrences: An increase in tumor marker levels after successful treatment can signal the return of the disease.
• Assessing prognosis: Some tumor markers can help predict the course of the disease and patient survival.
• Differential diagnosis: In some cases, tumor markers help distinguish malignant neoplasms from benign conditions.

It is important to remember that an elevated tumor marker level does not always mean cancer, and a normal level does not rule out its presence. Results should always be interpreted by a physician in conjunction with other diagnostic data.

Types of tumor markers: what do they show?

There are many different tumor markers, each associated with specific types of cancer or tissues. Here are some of the most well-known:

• PSA (Prostate-Specific Antigen): Used for the diagnosis and monitoring of prostate cancer. An increase in PSA can be associated not only with cancer, but also with benign prostatic hyperplasia, prostatitis, or trauma.
• CA-125: Associated with ovarian cancer. It can also be elevated in endometriosis, uterine fibroids, pelvic inflammatory disease, and even during menstruation.
• CA 15-3: Used to monitor breast cancer, especially in metastatic forms. It can be elevated in benign breast, liver, and lung diseases.
• CA 19-9: Used for pancreatic cancer, as well as bile duct and stomach cancer. It can be elevated in pancreatitis, cholecystitis, and liver cirrhosis.
• CEA (Carcinoembryonic Antigen): Associated with colorectal, lung, breast, and stomach cancer. It can be elevated in smokers, inflammatory bowel disease, and liver cirrhosis.
• AFP (Alpha-Fetoprotein): Used to diagnose liver cancer (hepatocellular carcinoma) and germ cell tumors. It is also elevated during pregnancy and certain benign liver diseases.
• hCG (Human Chorionic Gonadotropin): Used in the diagnosis of germ cell tumors (testicular, ovarian) and trophoblastic diseases. Known as a pregnancy marker.

Understanding tumor characteristics, such as melanoma [2], is crucial for choosing treatment tactics. Tumor markers help doctors obtain additional information about tumor behavior and response.

When are tumor marker tests prescribed?

Tumor marker tests are prescribed by a physician in strictly defined clinical situations. Self-prescribing these studies is not recommended, as it can lead to unnecessary anxiety or false conclusions. The main indications for tumor marker tests include:

• Suspicion of recurrence: After radical cancer treatment, regular monitoring of tumor markers can help timely detect the return of the disease.
• Assessing treatment effectiveness: During chemotherapy, radiation therapy, or targeted therapy, changes in tumor marker levels make it possible to judge how successfully the treatment is proceeding.
• Determining disease stage and prognosis: The level of certain tumor markers can correlate with tumor size, presence of metastases, and overall patient prognosis.
• Differential diagnosis: In some cases, when cancer is suspected but the diagnosis is unclear, tumor markers can help clarify it.
• Monitoring high-risk patients: In rare cases, with a very high genetic risk of developing a certain type of cancer, a doctor may recommend periodic monitoring of certain tumor markers. However, this is not screening for the general population.

Managing cancer patients, including the use of chemotherapy [3], requires an integrated approach where tumor markers play an auxiliary role, supplementing imaging data (ultrasound, CT, MRI) and biopsy data.

How to properly prepare for the test?

Proper preparation for blood donation for tumor markers is important for obtaining reliable results. Although general recommendations are similar to preparation for other biochemical blood tests, there may be specific requirements for certain markers. Collecting blood samples for biomarker analysis [4] is a standard procedure, but requires adherence to rules:

• Fasting: In most cases, blood is drawn in the morning on an empty stomach, after 8-12 hours of fasting. Drinking clean, non-carbonated water is permitted.
• Avoiding physical activity: Intensive physical activity should be excluded the day before the test.
• Excluding alcohol and smoking: It is recommended to refrain from alcohol and smoking 24 hours before the study.
• Reporting medications: Be sure to inform your doctor and nurse about all medications you are taking, as some of them can affect the results.
• Observing time intervals: For some tumor markers (e.g., PSA), it is important to observe time intervals after certain medical procedures (prostate biopsy, prostate massage, ultrasound). The doctor should give specific recommendations.
• Avoiding stress: Emotional stress can also affect certain indicators.

Always check with your attending physician or laboratory for specific preparation requirements for a particular tumor marker.

Interpretation of results: what is important to know?

Interpretation of tumor marker test results is a complex task that requires deep medical knowledge and should be performed only by an oncologist. It is important to consider the following aspects:

• Unspecificity: Elevated tumor marker levels can be caused not only by cancer, but also by benign diseases, inflammatory processes, injuries, and physiological conditions (e.g., pregnancy).
• False-negative results: A normal tumor marker level does not rule out the presence of cancer, especially in early stages. Some tumors may not produce tumor markers at all or produce them in negligible amounts.
• Dynamics are more important than absolute values: For disease monitoring, it is much more important to track changes in tumor marker levels dynamically than a single absolute value. A steady decrease or normalization after treatment is a good prognostic sign, while a persistent increase may indicate progression or recurrence.
• Integrated approach: Tumor marker results are always considered in combination with the clinical picture, instrumental study data (ultrasound, CT, MRI, PET-CT), biopsy results, and histological examination.
• Not for screening: With the exception of certain specific cases (e.g., PSA for prostate cancer screening in certain age groups, though debates exist here), tumor markers are not used for mass population screening due to their low specificity and sensitivity.

Do not panic when receiving elevated values and do not jump to conclusions. Discuss the results with your doctor, who can provide an adequate assessment and prescribe additional examinations if necessary.

Sources

1. Time for contrast to pass through the myocardium and its association with angina severity in patients with non-obstructive coronary artery disease. https://pubmed.ncbi.nlm.nih.gov/41572176/
2. Clinicopathologic Characteristics of Melanoma in Patients with Parkinson Disease. https://pubmed.ncbi.nlm.nih.gov/36876218/
3. Multiple sclerosis outcomes after cancer diagnosis in people with recorded chemotherapy exposure: A real-world MSBase study. https://pubmed.ncbi.nlm.nih.gov/42543909/
4. Feasibility of intra-day blood biomarker and ecological momentary assessment collection in multiple sclerosis. https://pubmed.ncbi.nlm.nih.gov/42570511/
5. Association of Biomarkers With Intracerebral Hematoma Expansion and Arterial Thromboembolic Events in Patients With Acute Intracranial Hemorrhage: The ANNEXA-I Biomarker Substudy. https://pubmed.ncbi.nlm.nih.gov/40289797/
6. The effectiveness of right-sided electrocardiogram in non-ST-segment elevation myocardial infarction. https://pubmed.ncbi.nlm.nih.gov/42036709/
7. Optical coherence tomography-derived macrophage arc as a novel biomarker for predicting adverse cardiovascular events in coronary artery disease: a multicentre study. https://pubmed.ncbi.nlm.nih.gov/42376680/
8. Real-world experience of ozanimod in adults with multiple sclerosis. https://pubmed.ncbi.nlm.nih.gov/41612670/

Disclaimer: The information in this article is for reference purposes only and does not replace professional medical advice. Always consult a qualified physician for diagnosis and treatment.