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What are tumor markers?
Tumor markers are
substances that are produced by cancer or by other cells of the body in
response to cancer or certain benign (noncancerous) conditions. Most tumor
markers are made by normal cells as well as by cancer cells; however, they are produced
at much higher levels in cancerous conditions. These substances can be
found in the blood, urine, stool, tumor
tissue, or other tissues
or bodily fluids of some
patients with cancer. Most tumor markers are proteins. However, more recently, patterns of gene expression and changes to DNA have also begun
to be used as tumor markers.
Many different tumor markers have been characterized and
are in clinical use. Some are associated with only one type of cancer, whereas
others are associated with two or more cancer types. No “universal” tumor
marker that can detect any type of cancer has been found.
There are some limitations to the use of tumor markers.
Sometimes, noncancerous conditions can cause the levels of certain tumor
markers to increase. In addition, not everyone with a particular type of cancer
will have a higher level of a tumor marker associated with that cancer.
Moreover, tumor markers have not been identified for every type of cancer.
How are tumor markers used in cancer care?
Tumor markers are
used to help detect, diagnose, and manage some types of cancer. Although an
elevated level of a tumor marker may suggest the presence of cancer, this alone
is not enough to diagnose cancer. Therefore, measurements of tumor markers are
usually combined with other tests, such as biopsies, to
diagnose cancer.
Tumor marker levels
may be measured before treatment to help doctors plan the appropriate therapy.
In some types of cancer, the level of a tumor marker reflects the stage
(extent) of the disease and/or the patient’s prognosis (likely outcome or
course of disease). More information about cancer staging is available on
the Staging page.
Tumor markers may also be measured periodically during
cancer therapy. A decrease in the level of a tumor marker or a return to the
marker’s normal level may indicate that the cancer is responding to treatment,
whereas no change or an increase may indicate that the cancer is not
responding.
Tumor markers may also be measured after treatment has
ended to check for recurrence (the return of cancer).
How are tumor markers measured?
A doctor takes a sample of tumor tissue or bodily fluid
and sends it to a laboratory, where various methods are used to measure the
level of the tumor marker.
If the tumor marker
is being used to determine whether treatment is working or whether there is
a recurrence, the
marker’s level will be measured in multiple samples taken over time. Usually
these “serial measurements,” which show whether the level of a marker is
increasing, staying the same, or decreasing, are more meaningful than a single
measurement.
Does NCI have guidelines for the use of tumor
markers?
NCI does not have such guidelines. However, some national
and international organizations do have guidelines for the use of tumor markers
for some types of cancer:
·
The American Society of Clinical Oncology
(ASCO) has published clinical
practice guidelinesExit Disclaimer on a variety of
topics, including tumor markers for breast cancer, colorectal cancer, lung
cancer, and others.
·
The National Academy of Clinical Biochemistry
publishes laboratory medicine practice guidelines, including Use
of Tumor Markers in Clinical Practice: Quality RequirementsExit Disclaimer, which
focuses on the appropriate use of tumor markers for specific cancers.
What tumor markers are currently being used,
and for which cancer types?
A number of tumor markers are currently being used for a
wide range of cancer types. Although most of these can be tested in
laboratories that meet standards set by the Clinical Laboratory Improvement
Amendments, some cannot be and may therefore be considered experimental. Tumor
markers that are currently in common use are listed below.
·
Tissue analyzed: Tumor
·
How used: To help determine treatment and
prognosis
Alpha-fetoprotein (AFP)
·
Tissue analyzed: Blood
·
How used: To help diagnose liver cancer and
follow response to treatment; to assess stage, prognosis, and response to
treatment of germ cell tumors
Beta-2-microglobulin (B2M)
·
How used: To determine prognosis and follow
response to treatment
Beta-human
chorionic gonadotropin (Beta-hCG)
·
Cancer types: Choriocarcinoma and germ cell tumors
·
Tissue analyzed: Urine or blood
·
How used: To assess stage, prognosis, and
response to treatment
·
Cancer type: Ovarian cancer
·
Tissue analyzed: Blood
·
Cancer type: Chronic
myeloid leukemia, acute
lymphoblastic leukemia, and acute
myelogenous leukemia
·
Tissue analyzed: Blood and/or bone marrow
·
How used: To confirm diagnosis, predict
response to targeted therapy, and monitor disease status
BRAF V600
mutations
·
Tissue analyzed: Tumor
·
How used: To select patients who are most
likely to benefit from treatment with certain targeted therapies
·
Tissue analyzed: Tumor
·
How used: To help in diagnosing and
determining treatment
CA15-3/CA27.29
·
Cancer type: Breast cancer
·
Tissue analyzed: Blood
·
How used: To assess whether treatment is
working or disease has recurred
CA19-9
·
Tissue analyzed: Blood
·
How used: To assess whether treatment is
working
·
Cancer type: Ovarian cancer
·
Tissue analyzed: Blood
·
Tissue analyzed: Blood
·
How used: To aid in diagnosis, check whether
treatment is working, and assess recurrence
Carcinoembryonic
antigen (CEA)
·
Cancer types: Colorectal cancer and some
other cancers
·
Tissue analyzed: Blood
·
How used: To keep track of how well cancer
treatments are working or check if cancer has come back
·
Tissue analyzed: Blood
·
How used: To determine whether treatment with
a targeted therapy is appropriate
Chromogranin
A (CgA)
·
Tissue analyzed: Blood
·
How used: To help in diagnosis, assessment of
treatment response, and evaluation of recurrence
Chromosomes 3, 7, 17, and 9p21
·
Cancer type: Bladder cancer
·
Tissue analyzed: Urine
·
How used: To help in monitoring for tumor
recurrence
·
Tissue analyzed: Blood
·
How used: To inform clinical decision making,
and to assess prognosis
Cytokeratin fragment
21-1
·
Cancer type: Lung cancer
·
Tissue analyzed: Blood
·
How used: To help in monitoring for
recurrence
·
Cancer type: Non-small cell lung cancer
·
Tissue analyzed: Tumor
·
How used: To help determine treatment and
prognosis
·
Cancer type: Breast cancer
·
Tissue analyzed: Tumor
·
How used: To determine whether treatment
with hormone
therapy and some targeted therapies is appropriate
Fibrin/fibrinogen
·
Cancer type: Bladder cancer
·
Tissue analyzed: Urine
·
How used: To monitor progression and response
to treatment
·
Cancer type: Ovarian cancer
·
Tissue analyzed: Blood
·
How used: To plan cancer treatment, assess
disease progression, and monitor for recurrence
·
Tissue analyzed: Tumor
·
How used: To determine whether treatment with
certain targeted therapies is appropriate
Immunoglobulins
·
Cancer types: Multiple myeloma and Waldenström macroglobulinemia
·
Tissue analyzed: Blood and urine
·
How used: To help diagnose disease, assess
response to treatment, and look for recurrence
KRAS gene
mutation analysis
·
Cancer types: Colorectal cancer and non-small
cell lung cancer
·
Tissue analyzed: Tumor
·
How used: To determine whether treatment with
a particular type of targeted therapy is appropriate
·
Cancer types: Germ cell tumors, lymphoma,
leukemia, melanoma, and neuroblastoma
·
Tissue analyzed: Blood
·
How used: To assess stage, prognosis, and
response to treatment
Neuron-specific enolase (NSE)
·
Cancer types: Small cell lung cancer and
neuroblastoma
·
Tissue analyzed: Blood
·
How used: To help in diagnosis and to assess
response to treatment
Nuclear matrix protein 22
·
Cancer type: Bladder cancer
·
Tissue analyzed: Urine
·
How used: To monitor response to treatment
Programmed death ligand 1 (PD-L1)
·
Cancer type: Non-small cell lung cancer
·
Tissue analyzed: Tumor
·
How used: To determine whether treatment with
a particular type of targeted therapy is appropriate
·
Cancer type: Prostate cancer
·
Tissue analyzed: Blood
·
How used: To help in diagnosis, assess
response to treatment, and look for recurrence
·
Cancer type: Thyroid cancer
·
Tissue analyzed: Blood
·
How used: To evaluate response to treatment
and look for recurrence
Urokinase plasminogen
activator (uPA) and plasminogen activator inhibitor (PAI-1)
·
Cancer type: Breast cancer
·
Tissue analyzed: Tumor
·
How used: To determine aggressiveness of
cancer and guide treatment
5-Protein signature (OVA1®)
·
Cancer type: Ovarian cancer
·
Tissue analyzed: Blood
·
How used: To pre-operatively assess pelvic
mass for suspected ovarian cancer
21-Gene signature (Oncotype DX®)
·
Cancer type: Breast cancer
·
Tissue analyzed: Tumor
·
How used: To evaluate risk of recurrence
70-Gene signature (Mammaprint®)
·
Cancer type: Breast cancer
·
Tissue analyzed: Tumor
·
How used: To evaluate risk of recurrence
Can tumor markers be used in cancer
screening?
Because tumor markers
can be used to assess the response of a tumor to treatment and for prognosis,
researchers have hoped that they might also be useful in screening tests that
aim to detect cancer early, before there are any symptoms. For a screening test
to be useful, it should have very high sensitivity (ability to correctly
identify people who have the disease) and specificity (ability to correctly
identify people who do not have the
disease). If a test is highly sensitive, it will identify most people with the
disease—that is, it will result in very few false-negative results. If a test
is highly specific, only a small number of people will test positive for the
disease who do not have it—in other words, it will result in very few
false-positive results.
Although tumor markers are extremely useful in
determining whether a tumor is responding to treatment or assessing whether it
has recurred, no tumor marker identified to date is sufficiently sensitive or
specific to be used on its own to screen for cancer.
For example,
the prostate-specific
antigen (PSA) test, which measures the level of PSA in the
blood, is often used to screen men for prostate cancer. However, an increased
PSA level can be caused by benign prostate conditions as well as by prostate
cancer, and most men with an elevated PSA level do not have prostate cancer.
Initial results from two large randomized controlled
trials, the NCI-sponsored Prostate, Lung, Colorectal, and
Ovarian Cancer Screening Trial (PLCO), and the European Randomized Study of
Screening for Prostate Cancer, showed that PSA testing at best leads to only a
small reduction in the number of prostate cancer deaths. Moreover, it is not
clear whether the benefits of PSA screening outweigh the harms of follow-up
diagnostic tests and treatments for cancers that in many cases would never have
threatened a man’s life.
Similarly, results
from the PLCO trial showed that CA-125, a tumor
marker that is sometimes elevated in the blood of women with ovarian cancer but
can also be elevated in women with benign conditions, is not sufficiently
sensitive or specific to be used together with transvaginal ultrasound to screen for ovarian
cancer in women at average risk of the disease. An analysis of 28 potential
markers for ovarian cancer in blood from women who later went on to develop
ovarian cancer found that none of these markers performed even as well as
CA-125 at detecting the disease in women at average risk.
What kind of research is under way to develop
more accurate tumor markers?
Cancer researchers
are turning to proteomics (the
study of protein structure, function, and patterns of expression) in hopes of
developing new biomarkers that
can be used to identify disease in its early stages, to predict the
effectiveness of treatment, or to predict the chance of cancer recurrence after
treatment has ended.
Scientists are also
evaluating patterns of gene
expression for their ability to help determine a
patient’s prognosis or response to therapy. For example, results of the
NCI-sponsored Trial Assigning IndividuaLized Options for
Treatment (Rx), or TAILORx , showed that for women recently diagnosed
with lymph node–negative, hormone receptor–positive, HER2-negative breast
cancer who had undergone surgery, those with the lowest 21-gene (Oncotype Dx®)
recurrence scores had very low recurrence rates when given hormone therapy
alone and thus can be spared chemotherapy. The trial is ongoing to see whether
women at intermediate risk of recurrence, based on the 21-gene test, do better
with chemotherapy in addition to hormone therapy than with hormone therapy alone.
More information on
NCI’s role in supporting research on novel tools and methods for diagnosing
cancer is available on the Diagnosis research
page.
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