Tumor Marker Tests

Tumor marker tests are performed to measure the presence or levels of specific substances produced by cancer cells or by the body in response to cancer. These markers are often proteins that can be detected in the blood, urine, or tissues. Tumor marker tests are used for diagnosing cancer, monitoring treatment response, and detecting the recurrence of cancer.

Types of Tumor Markers

Some of the common types of tumor markers include:

• PSA (prostate-specific antigen): Used for prostate cancer screening or monitoring
• CA-125: Used for ovarian cancer monitoring
• CEA (carcinoembryonic antigen): Associated with colorectal and other cancers
• AFP (alpha-fetoprotein): Elevated in some liver and testicular cancers
• CA 15-3 and CA 27.29: Used for monitoring breast cancer
• CA 19-9: Elevated in pancreatic, colorectal, and other cancers

Indications 

Tumor marker tests are commonly used to:

• Diagnose cancer
• Check for cancer in individuals who have a strong family history of a specific cancer but do not exhibit symptoms (screening)
• Predict how aggressive the cancer is likely to be
• Check how far the cancer has spread (staging)
• Predict which treatment the cancer is likely to respond to
• Predict how likely it is that the cancer will recur after treatment
• Determine if the current cancer treatment is working, or see if the cancer has returned after treatment

It is important to note that the presence of tumor markers alone is not sufficient for a definitive cancer diagnosis. These tests are typically used in conjunction with other diagnostic tools such as imaging studies, biopsies, and clinical evaluations, in order to form a comprehensive diagnostic picture.

Preparation

Tumor marker tests are usually performed in a lab or hospital setting. There are usually no special preparations needed for these tests.

Procedure

The process for performing a tumor marker test generally involves the following steps:

• Blood is the most common sample for tumor marker testing. A healthcare professional will use a needle to draw blood from a vein, usually in the arm. In some cases, other samples such as urine or tissue may be collected.
• The collected sample is sent to a laboratory for analysis. In the lab, the sample is processed to extract the relevant components, such as plasma or serum for blood-based tests.
• Many tumor marker tests use immunoassay techniques. In immunoassays, specific antibodies are used to detect and quantify the targeted tumor marker in the sample. Other techniques, such as polymerase chain reaction (PCR) or mass spectrometry, may be used depending on the marker.
• The laboratory equipment measures the concentration of the tumor marker in the sample. The results are typically reported in units such as nanograms per milliliter (ng/mL) or international units per milliliter (IU/mL).
• The healthcare provider interprets the results in the context of the patient's overall clinical picture. Values within the normal range are considered typical for a healthy individual, while values outside the normal range may be considered abnormal. Elevated levels of a tumor marker may prompt further diagnostic tests, such as imaging studies or biopsies, to confirm or rule out the presence of cancer.

Post-procedure care

In general, there is no specific post-procedure care required for tumor marker tests.  Most patients can resume their normal activities immediately after testing.

Limitations of Tumor Marker Tests

Tumor marker tests have several limitations that need to be considered when interpreting results. These limitations include:

• A disease or condition that is not cancer can also raise tumor marker levels.
• Tumor markers can go up and down over time, making it hard to measure them consistently.
• The level of a tumor marker may not go up until after the cancer is advanced, making early detection of cancer difficult.
• Some cancers do not make tumor markers that are found in the blood, and some types of cancer have no known tumor markers.
• Some individuals do not have higher tumor marker levels even when the type of cancer they have normally makes tumor markers.

Summary

It is crucial to emphasize that an elevated level of tumor marker does not necessarily indicate cancer, and normal levels do not rule out the possibility of cancer. Tumor marker tests are part of a broader diagnostic process and are used in conjunction with other clinical information to guide patient care. The interpretation of results and subsequent actions are determined by healthcare professionals based on the specific circumstances of each individual.