Tumor marker

Tumor marker

Tumor markers are molecules present in blood or other body fluids that may indicate the presence of cancer in an individual. These markers can be derived from cancer cells themselves or produced by the body in response to malignant conditions.

Tumor cell clusters from ascites fluid: nuclei colored in blue, tumor-specific markers colored in red and green

Origin and Composition

Most tumor markers originate from both cancerous and non-cancerous cells. However, in the presence of cancer, these markers are typically found in elevated concentrations. While the majority of tumor markers are proteins, recent scientific advancements have identified patterns in gene expression and DNA alterations as potential markers.

Specificity and Universality

A variety of tumor markers have been discovered, with some being specific to a particular type of cancer, while others can be associated with multiple cancers. Currently, no singular tumor marker exists that can detect every form of cancer.

Limitations

There are inherent limitations in solely relying on tumor markers for cancer detection:

• Non-malignant conditions can also elevate tumor marker levels.
• Not every individual with a specific cancer will exhibit raised levels of the associated tumor marker.
• Some cancers may not have an identifiable associated tumor marker.

Clinical Uses

Detection and Diagnosis

Though an elevated tumor marker can indicate potential malignancy, it is insufficient for a definitive cancer diagnosis. Consequently, tumor marker measurements are usually employed in conjunction with other diagnostic tests, like biopsies, to ascertain the presence of cancer.

Treatment Planning

Prior to initiating treatment, tumor marker levels can be assessed to assist medical professionals in devising an effective treatment strategy. In some instances, the concentration of a tumor marker can give insights into the stage of the cancer and the patient's prognosis.

Monitoring Treatment Efficacy

During the course of treatment, periodic measurement of tumor markers can provide valuable feedback. A decline or return to normalcy of the marker level can suggest a positive response to treatment. Conversely, stagnation or an increase can indicate non-responsiveness to the therapy.

Post-treatment Surveillance

Post-treatment, tumor markers can be used as surveillance tools to monitor for potential cancer recurrence.

Measurement Process

To measure tumor markers, a sample of tumor tissue or a bodily fluid is procured and forwarded to a laboratory. In the laboratory, specialized techniques are employed to quantify the marker level. When tracking treatment progress or checking for recurrence, serial measurements are often more insightful than a singular reading, as they can capture the trend in marker levels over a duration.

Testing Standards

Most of the tumor markers are tested in laboratories that comply with the standards of the Clinical Laboratory Improvement Amendments (CLIA). Some markers, however, remain experimental and aren't tested under these standards.

Applications

Tumor markers have various clinical applications:

Diagnosis: While they are not usually specific enough for diagnostic purposes alone, when combined with other tests, they can help to pinpoint a diagnosis. Prognosis: They can provide information about how aggressive a cancer is, which can help determine the best treatment approach. Treatment Decisions: Some tumor markers indicate how likely a tumor is to respond to certain treatments. Monitoring: Tracking levels over time can help doctors assess how well treatment is working or if cancer has returned.

Limitations

While tumor markers offer significant benefits, they are not without limitations. Not every type of cancer has an associated marker, and even when markers are present, they might not be found in every patient with that cancer. Additionally, non-cancerous conditions can sometimes cause the levels of tumor markers to increase. Hence, tumor markers are usually used in conjunction with other tests for accuracy.

Experimental Tumor Markers

There are numerous potential tumor markers under investigation that may, in the future, offer more precise and individualized ways to diagnose and manage cancer. These experimental markers aren't yet approved for routine clinical use and are typically found in the realm of clinical trials.

List of tumor markers

Tumor markers in common use include:

ALK gene

ALK gene rearrangements and overexpression

• Cancer types: Non-small cell lung cancer and anaplastic large cell lymphoma
• Tissue analyzed: Tumor
• Purpose: For treatment and prognosis determination

Alpha-fetoprotein (AFP)

• Cancer types: Liver cancer and germ cell tumors
• Tissue analyzed: Blood
• Purpose: Diagnose liver cancer, track response to treatment, and assess germ cell tumors' stage, prognosis, and treatment response

Beta-2-microglobulin (B2M)

• Cancer types: Multiple myeloma, chronic lymphocytic leukemia, and some lymphomas
• Tissue analyzed: Blood, urine, or cerebrospinal fluid
• Purpose: Determine prognosis and track treatment response
• Beta-human chorionic gonadotropin (Beta-hCG)
• Cancer types: Choriocarcinoma and germ cell tumors
• Tissue analyzed: Urine or blood
• Purpose: Assess stage, prognosis, and treatment response

BRCA1 and BRCA2 gene mutations

• Cancer type: Ovarian cancer
• Tissue analyzed: Blood
• Purpose: Determine if a specific targeted therapy treatment is appropriate
• BCR-ABL fusion gene (Philadelphia chromosome)
• Cancer types: Chronic myeloid leukemia, acute lymphoblastic leukemia, and acute myelogenous leukemia
• Tissue analyzed: Blood and/or bone marrow
• Purpose: Confirm diagnosis, anticipate targeted therapy response, and monitor disease status

BRAF V600 mutations

• Cancer types: Cutaneous melanoma and colorectal cancer
• Tissue analyzed: Tumor
• Purpose: Select patients suitable for certain targeted therapies

C-kit/CD117

• Cancer types: Gastrointestinal stromal tumor and mucosal melanoma
• Tissue analyzed: Tumor
• Purpose: Aid diagnosis and determine treatment

CA15-3 / CA27.29

• Cancer type: Breast cancer
• Tissue analyzed: Blood
• Purpose: Evaluate treatment efficacy or detect disease recurrence

CA19-9

• Cancer types: Pancreatic cancer, gallbladder cancer, bile duct cancer, and gastric cancer
• Tissue analyzed: Blood
• Purpose: Assess treatment efficacy

CA-125

• Cancer type: Ovarian cancer
• Tissue analyzed: Blood
• Purpose: Aid diagnosis, evaluate treatment response, and monitor for recurrence

Calcitonin

• Cancer type: Medullary thyroid cancer
• Tissue analyzed: Blood
• Purpose: Support diagnosis, assess treatment efficacy, and detect recurrence

Carcinoembryonic antigen (CEA)

• Cancer types: Colorectal cancer and some other cancers
• Tissue analyzed: Blood
• Purpose: Track cancer treatment efficacy or check for recurrence

==Programmed death ligand 1 (PD-L1

• Cancer type: Non-small cell lung cancer
• Tissue analyzed: Tumor
• How used: To determine potential response to immunotherapy agents that target the PD-1/PD-L1 pathway.
• [Prostate-specific antigen]

PSA

• Cancer type: Prostate cancer
• Tissue analyzed: Blood
• How used: To monitor for recurrence, track treatment progress, and early detection of prostate cancer in conjunction with a digital rectal exam.
• RET gene mutations
• Cancer type: Medullary thyroid cancer
• Tissue analyzed: Tumor
• How used: To help in diagnosis and guiding targeted therapies.

S100

• Cancer type: Melanoma
• Tissue analyzed: Blood
• How used: To monitor treatment response and detect recurrence early.
• [Thyroglobulin]
• Cancer type: Differentiated thyroid cancer
• Tissue analyzed: Blood
• How used: To monitor treatment success and detect any possible recurrence.

TP53

TP53 ([p53]) gene mutations

• Cancer types: Various types including Breast cancer, Ovarian cancer, and Colorectal cancer
• Tissue analyzed: Tumor
• How used: To predict prognosis and potential response to treatment.

Urokinase plasminogen activator

• Urokinase plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1)
• Cancer type: Breast cancer
• Tissue analyzed: Tumor
• How used: To determine prognosis and aid in determining treatment approach.

Vascular endothelial growth factor

• VEGF] (Vascular endothelial growth factor)
• Cancer types: Various, especially cancers that are more vascular such as Renal cell carcinoma
• Tissue analyzed: Blood
• How used: To evaluate potential for anti-angiogenic therapies.

See Also

• Cancer staging
• Biopsy
• Protein
• DNA

Tumor marker Resources
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