The following is extracted from the American Cancer Society’s web site: http://www.cancer.org/docroot/PED/content/PED_2_3X_Tumor_Markers.asp?sitearea=PED:
Tumor markers are substances that can be found in the body when cancer is present. They are usually found in the blood or urine. They can be products of the cancer cells themselves or of the body in response to cancer or other conditions. Most tumor markers are proteins.
There are many different tumor markers. Some are seen only in a single type of cancer, while others can be found in many types of cancer.
To test for a tumor marker, the doctor sends a sample of the patient's blood or urine to a lab. The marker is usually found by combining the blood or urine with manmade antibodies designed to react with that specific protein.
For many reasons, tumor markers by themselves are usually not enough to diagnose or rule out cancer. Most tumor markers can be made by normal cells as well as by cancer cells. Sometimes, non-cancerous diseases can also cause levels of certain tumor markers to be higher than normal. And not every person with cancer may have higher levels of a tumor marker.
For these reasons, only a handful of tumor markers are commonly used by most doctors. When a doctor looks at the level of a certain tumor marker, he or she will consider it along with the results of the patient's history & physical exam and other lab tests or imaging tests.
How Are Tumor Markers Used?
Screening & Early Detection of Cancer
Screening refers to looking for cancer in people who have no symptoms of the disease. Early detection is finding cancer at an early stage, when it is less likely to have spread & is more likely to respond well to treatment. Although tumor markers were first developed to test for cancer in people without symptoms, very few markers have been shown to be helpful in this way.
The most widely accepted tumor marker is the prostate-specific antigen (PSA) blood test, which is used (along with the digital rectal exam) to screen for prostate cancer. But because it's not always clear what the test results mean, not all doctors agree that PSA screening is appropriate for all men. Newer versions of the PSA test may prove to be more accurate.
Most other tumor markers have not been shown to detect cancer much earlier than they would have been found otherwise...
Determining the Effectiveness of Cancer Treatment
One of the most important uses for tumor markers is to monitor patients being treated for cancer, especially advanced cancer. If a tumor marker is available for a specific type of cancer, it is much easier to measure it to see if the treatment is working rather than repeating chest x-rays, CT scans, bone scans, or other tests. It also tends to be less expensive.
If the tumor marker level in the blood goes down, it is almost always a sign that the treatment is having an effect. On the other hand, if the marker level goes up, then the treatment probably should be changed. (One exception is if the cancer is very sensitive to a certain chemotherapy treatment. In this case, the chemotherapy can cause many cancer cells to die & release large amounts of the marker into the blood, which will cause the level of the tumor marker to rise for a short time.)
Detecting Recurrent Cancer
Markers are also used to look for cancer that may come back (recur) after initial treatment. Some tumor markers may be useful once treatment is complete and there is no evidence of cancer remaining…
Some women who have been treated for breast cancer have yearly blood tests for levels of the tumor marker CA 15-3. This can sometimes detect cancer recurrence before the woman has symptoms or evidence of cancer on imaging tests. Many doctors question the test's value, though, because no one has shown a long-term advantage in finding recurrent breast cancer early. And usually the cancer causes symptoms or can be found by the doctor around the same time that the CA 15-3 level rises…
Because of this, some doctors & medical groups do not recommend using these tumor markers after treatment aimed at curing these cancers. They are more likely to be used to monitor more advanced cancer, especially when treatment may not be expected to result in a cure, as mentioned above…
Specific [Breast Cancer] Tumor Markers
CA 15-3: CA 15-3 is used mainly to monitor patients with breast cancer. Elevated blood levels are found in less than 10% of patients with early disease and in about 70% of patients with advanced disease. Levels usually drop following effective treatment, although they may spike in the first few weeks after treatment is started, a result of dying cancer cells spilling their contents into the bloodstream.
The normal level is usually less than 25 U/mL (units/milliliter), depending on the lab. But levels as high as 100 U/mL can sometimes be seen in women who do not have cancer. Levels of this marker can also be higher in other cancers and in some non-cancerous conditions such as benign breast conditions and hepatitis.
CA 27.29: CA 27.29 is another marker used to follow patients with breast cancer during or after treatment. This test measures the same marker as the CA 15-3 test, but in a different way. Although it is a newer test than CA 15-3, it does not appear to be any better in detecting either early or advanced disease. It may be less likely to be positive in people without cancer. The normal level is usually less than 38 to 40 U/mL (units/milliliter), depending on the testing lab. This marker can also be elevated in other cancers and in some non-cancerous conditions, and it may not be elevated in some women with breast cancer… (This is the tumor marker I have measured & report)
Estrogen receptors/progesterone receptors: Breast tumor samples--not blood samples--from women and men with breast cancer are commonly tested for these markers. Breast cancers that contain estrogen receptors are often referred to as "ER-positive," while those with progesterone receptors are "PR-positive." About 7 out of 10 breast cancers test positive for at least one of these markers. These cancers tend to have a better prognosis than cancers without these receptors and are much more likely to respond to hormonal therapy such as tamoxifen or aromatase inhibitors… (As I mentioned in my chapter 5 blog, my cancer is “ER positive;” it is also “PR positive.” In my chapter 11 blog, I discuss the fact that we chose hormone therapy with an aromatase inhibitor.)
. . .
No tumor marker has been found to be useful for screening or for the diagnosis of early stage breast cancer.
At the time of diagnosis, breast cancer tissue is often tested for estrogen and progesterone receptors, as well as the HER2/neu antigen. These markers provide some information on how aggressive the cancer may be & how likely it is to respond to certain treatments.
The markers most commonly used to follow patients with advanced cancer or to detect recurrence are CA 15-3 & CEA. The CA 27.29 test is also used by some doctors. The CA 15-3 & CA 27.29 are probably equally sensitive, while the CEA is less sensitive.
These markers are most useful in measuring the results of treatment for patients with advanced disease. Generally speaking, blood levels go down if the cancer responds to treatment & rise if the cancer progresses.
Some doctors use these tests to look for signs of recurrence in women who have no symptoms of cancer after their first treatment. But most professional groups do not recommend using these markers to follow women already treated for early stage disease…
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I hope this helps you to have a better understanding of tumor markers.
Tumor markers are substances that can be found in the body when cancer is present. They are usually found in the blood or urine. They can be products of the cancer cells themselves or of the body in response to cancer or other conditions. Most tumor markers are proteins.
There are many different tumor markers. Some are seen only in a single type of cancer, while others can be found in many types of cancer.
To test for a tumor marker, the doctor sends a sample of the patient's blood or urine to a lab. The marker is usually found by combining the blood or urine with manmade antibodies designed to react with that specific protein.
For many reasons, tumor markers by themselves are usually not enough to diagnose or rule out cancer. Most tumor markers can be made by normal cells as well as by cancer cells. Sometimes, non-cancerous diseases can also cause levels of certain tumor markers to be higher than normal. And not every person with cancer may have higher levels of a tumor marker.
For these reasons, only a handful of tumor markers are commonly used by most doctors. When a doctor looks at the level of a certain tumor marker, he or she will consider it along with the results of the patient's history & physical exam and other lab tests or imaging tests.
How Are Tumor Markers Used?
Screening & Early Detection of Cancer
Screening refers to looking for cancer in people who have no symptoms of the disease. Early detection is finding cancer at an early stage, when it is less likely to have spread & is more likely to respond well to treatment. Although tumor markers were first developed to test for cancer in people without symptoms, very few markers have been shown to be helpful in this way.
The most widely accepted tumor marker is the prostate-specific antigen (PSA) blood test, which is used (along with the digital rectal exam) to screen for prostate cancer. But because it's not always clear what the test results mean, not all doctors agree that PSA screening is appropriate for all men. Newer versions of the PSA test may prove to be more accurate.
Most other tumor markers have not been shown to detect cancer much earlier than they would have been found otherwise...
Determining the Effectiveness of Cancer Treatment
One of the most important uses for tumor markers is to monitor patients being treated for cancer, especially advanced cancer. If a tumor marker is available for a specific type of cancer, it is much easier to measure it to see if the treatment is working rather than repeating chest x-rays, CT scans, bone scans, or other tests. It also tends to be less expensive.
If the tumor marker level in the blood goes down, it is almost always a sign that the treatment is having an effect. On the other hand, if the marker level goes up, then the treatment probably should be changed. (One exception is if the cancer is very sensitive to a certain chemotherapy treatment. In this case, the chemotherapy can cause many cancer cells to die & release large amounts of the marker into the blood, which will cause the level of the tumor marker to rise for a short time.)
Detecting Recurrent Cancer
Markers are also used to look for cancer that may come back (recur) after initial treatment. Some tumor markers may be useful once treatment is complete and there is no evidence of cancer remaining…
Some women who have been treated for breast cancer have yearly blood tests for levels of the tumor marker CA 15-3. This can sometimes detect cancer recurrence before the woman has symptoms or evidence of cancer on imaging tests. Many doctors question the test's value, though, because no one has shown a long-term advantage in finding recurrent breast cancer early. And usually the cancer causes symptoms or can be found by the doctor around the same time that the CA 15-3 level rises…
Because of this, some doctors & medical groups do not recommend using these tumor markers after treatment aimed at curing these cancers. They are more likely to be used to monitor more advanced cancer, especially when treatment may not be expected to result in a cure, as mentioned above…
Specific [Breast Cancer] Tumor Markers
CA 15-3: CA 15-3 is used mainly to monitor patients with breast cancer. Elevated blood levels are found in less than 10% of patients with early disease and in about 70% of patients with advanced disease. Levels usually drop following effective treatment, although they may spike in the first few weeks after treatment is started, a result of dying cancer cells spilling their contents into the bloodstream.
The normal level is usually less than 25 U/mL (units/milliliter), depending on the lab. But levels as high as 100 U/mL can sometimes be seen in women who do not have cancer. Levels of this marker can also be higher in other cancers and in some non-cancerous conditions such as benign breast conditions and hepatitis.
CA 27.29: CA 27.29 is another marker used to follow patients with breast cancer during or after treatment. This test measures the same marker as the CA 15-3 test, but in a different way. Although it is a newer test than CA 15-3, it does not appear to be any better in detecting either early or advanced disease. It may be less likely to be positive in people without cancer. The normal level is usually less than 38 to 40 U/mL (units/milliliter), depending on the testing lab. This marker can also be elevated in other cancers and in some non-cancerous conditions, and it may not be elevated in some women with breast cancer… (This is the tumor marker I have measured & report)
Estrogen receptors/progesterone receptors: Breast tumor samples--not blood samples--from women and men with breast cancer are commonly tested for these markers. Breast cancers that contain estrogen receptors are often referred to as "ER-positive," while those with progesterone receptors are "PR-positive." About 7 out of 10 breast cancers test positive for at least one of these markers. These cancers tend to have a better prognosis than cancers without these receptors and are much more likely to respond to hormonal therapy such as tamoxifen or aromatase inhibitors… (As I mentioned in my chapter 5 blog, my cancer is “ER positive;” it is also “PR positive.” In my chapter 11 blog, I discuss the fact that we chose hormone therapy with an aromatase inhibitor.)
. . .
No tumor marker has been found to be useful for screening or for the diagnosis of early stage breast cancer.
At the time of diagnosis, breast cancer tissue is often tested for estrogen and progesterone receptors, as well as the HER2/neu antigen. These markers provide some information on how aggressive the cancer may be & how likely it is to respond to certain treatments.
The markers most commonly used to follow patients with advanced cancer or to detect recurrence are CA 15-3 & CEA. The CA 27.29 test is also used by some doctors. The CA 15-3 & CA 27.29 are probably equally sensitive, while the CEA is less sensitive.
These markers are most useful in measuring the results of treatment for patients with advanced disease. Generally speaking, blood levels go down if the cancer responds to treatment & rise if the cancer progresses.
Some doctors use these tests to look for signs of recurrence in women who have no symptoms of cancer after their first treatment. But most professional groups do not recommend using these markers to follow women already treated for early stage disease…
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