What Are Mesothelioma Blood Tests?
Blood tests for mesothelioma aim to detect substances cancer cells produce. These substances are called biomarkers. Currently blood tests alone are not accurate enough to diagnose mesothelioma.
While a direct blood test for mesothelioma does not yet exist, blood tests can show possible indicators of cancer. Instead of relying solely on mesothelioma blood tests, doctors also use detailed imaging scans as well as tissue biopsies. Looking at all of these results together, doctors can better confirm a diagnosis of asbestos-related illnesses.
There is also no blood test that can detect if someone was exposed to asbestos. Biopsy tests of tissues, however, can reveal the presence of asbestos fibers that can get stuck in tissues. Biopsies are often used when cancer is suspected.
Mesothelioma survivor Chris Shelton discovered he had cancer while hospitalized for more than a month after a serious motorcycle accident. He had many blood tests during this time to monitor his recovery and overall health.
“The doctor came into my hospital room and said he had good news and bad news,” Shelton recalled. “He said, ‘You’ll walk again, but your blood work makes us think you have some sort of cancer.’” Eventually, after much more testing, Shelton received a diagnosis of mesothelioma.
How Do Mesothelioma Blood Tests Work?
Mesothelioma blood tests screen for biomarkers, which are proteins and other things found in blood and tissue that can indicate health statuses. For example, blood sugar and hemoglobin A1C are useful indicators to diagnose diabetes and monitor treatment. Cancer cells produce certain proteins that circulate in the blood.
For some tumors, biomarker proteins are unique to that specific cancer. Identifying them in a blood test indicates that a person may have that cancer. The biomarkers for mesothelioma are also present in healthy people but are higher when mesothelioma exists. However, these tests are not always accurate, so it is not definitive proof of a diagnosis.
Blood tests can help confirm a diagnosis of mesothelioma and rule out other cancers. Many cancers originate in the lungs or spread to the lungs from other parts of the body. Different cancers express different immunohistochemical markers — proteins that labwork can identify by using antibodies.
There are no biomarkers specific to mesothelioma, but levels of the proteins calretinin, cytokeratin 5 and 5/6, WT-1, podoplanin (D2-40) and mesothelin are useful in identifying possible mesothelioma.
As Dr. Snehal Smart of The Mesothelioma Center explained, blood tests can “help find mesothelioma in a patient before symptoms can even be seen.” Blood tests such as MESOMARK look for a particular protein – the SMRP protein.
Smart said this protein is “usually high in patients who have mesothelioma.” Therefore, while a blood test such as a MESOMARK assay cannot be enough to diagnose a patient on its own, “high levels of the SMRP protein can indicate a probable diagnosis of mesothelioma.”
Common Mesothelioma Blood Tests
Three blood tests are commonly used to help diagnose mesothelioma: the MESOMARK assay, N-ERC/mesothelin test and fibulin-3 test. Each test has strengths and weaknesses, but they all can help doctors accurately diagnose mesothelioma when used with biopsies and imaging studies.
For a blood test to be useful for diagnosis it must be sensitive and/or specific. A test with high sensitivity is better at detecting mesothelioma. A test with high specificity can help rule out mesothelioma. Some tests are more sensitive than specific and vice versa.
For example, the N-ERC/mesothelin test is very sensitive but not very specific. When N-ERC/mesothelin levels are high, there’s a high likelihood that mesothelioma is present. However, a person may still have mesothelioma even if their N-ERC/mesothelin levels are low.
The fibulin-3 test, on the other hand, is very specific for mesothelioma. If fibulin-3 levels are low, there is very little chance of having mesothelioma. In other words, the N-ERC/mesothelin test can detect mesothelioma most of the time, while the fibulin-3 test can usually tell if you don’t have mesothelioma.
The performance of all of these blood tests requires a technique called ELISA. Medical professionals collect a blood sample and send it to the laboratory where it is mixed with antibodies that target a specific biomarker. Using sophisticated equipment, the lab can then determine the levels of biomarkers in the blood.
The MESOMARK assay is a test that can detect most types of mesothelioma as well as see how well treatment is working.
The MESOMARK assay measures serum-measured soluble mesothelin-related peptides. These are proteins made by mesothelial cells. Healthy cells produce low levels of SMRP, but high SMRP levels may show the presence of mesothelioma. As treatment progresses, SMRP levels decrease.
“A MESOMARK blood test is performed by the physician or nurse practitioner drawing a sample of blood,” said Smart. “That blood is sent to a lab where the levels of SMRP protein are measured.”
Some types of mesothelioma, such as sarcomatoid tumors, do not release high levels of SMRP. This is why the U.S. Food and Drug Administration recommends that doctors combine the MESOMARK assay with other tests to ensure an accurate mesothelioma diagnosis.
Some insurance companies do not cover this blood test. If you have a history of asbestos exposure, ask your doctor if the MESOMARK blood test would be helpful.
The N-ERC/mesothelin test detects a specific form of mesothelin called N-ERC/mesothelin. The test is similar to MESOMARK but looks for a specific version of the mesothelin molecule, which increases the test’s accuracy.
The test is 95% effective at detecting mesothelioma. However, because several other types of cancer also increase mesothelin levels, it is only 76% effective at ruling out mesothelioma. This test is more accurate than MESOMARK but, like other blood tests, cannot be used to diagnose mesothelioma on its own.
Mesothelioma cells produce a protein called fibulin-3. Specific tests can detect this protein in pleural fluid and blood. Mesothelioma specialist Dr. Harvey Pass helped develop it for diagnosis.
He co-authored a study showing that the test is 96.7% effective at detecting mesothelioma. It is also 95.5% effective at ruling it out in people without the disease.
Several researchers have found that the sensitivity of the fibulin-3 test can vary. This potentially makes the test less effective for detecting mesothelioma. However, it is still extremely effective in ruling out mesothelioma.
Research also shows that fibulin-3 levels are higher in people with known asbestos exposure. This means that the fibulin-3 test is very good at determining whether an individual has had significant asbestos exposure.
Additionally, fibulin-3 levels can help predict mesothelioma prognosis. Very high levels indicate a worse prognosis. Fibulin-3 testing is extremely useful when combined with other mesothelioma blood tests.
Emerging Biomarker-Based Blood Tests
As researchers discover more about mesothelioma, they are finding new biomarkers that may improve mesothelioma diagnosis and treatment. New biomarker tests can help medical professionals diagnose mesothelioma, distinguish it from other cancers, predict disease prognosis, select the most effective treatment and monitor treatment progression.
Discovering new biomarkers is important in understanding how mesothelioma develops. Some biomarkers are proteins that are involved in how cells become cancerous, such as YAP, a protein that interacts with DNA. These biomarkers can reveal new targets for therapies, such as immunotherapy.
- 8-Hydroxy-2′-Deoxyguanosine: 8OHdG, like fibulin-3, is higher in people who have been exposed to asbestos. It may be useful in identifying people at higher risk of mesothelioma and other cancers.
- Calretinin: Mesothelioma raises calretinin levels — the epithelioid type more than the sarcomatoid type. When combined with mesothelin tests, calretinin tests can help improve mesothelioma diagnosis accuracy and distinguish it from other asbestos-related diseases.
- Epidermal Growth Factor Receptor: EGFR levels are increased in mesothelioma (especially the epithelioid type) and some other lung cancers. EGFR may play a role in the development of mesothelioma. Clinical trials of mesothelioma treatments that target EGFR are ongoing.
- Estrogen Receptor-β: ER-β levels are elevated in some cases of mesothelioma. Research shows that people with mesothelioma who had high to moderate levels of ER-β responded better to chemotherapy and had better survival rates. Drugs that target ER-β can improve how well chemotherapy works.
- Megakaryocyte Potentiation Factor: Mesothelioma raises MPF levels. Like mesothelin, levels can decrease after surgery. This makes it useful to track treatment progress. When combined with tests for mesothelin and calretinin, MPF may be useful to help diagnose mesothelioma.
- Osteopontin: Research shows that osteopontin levels are higher in cases of both pleural and peritoneal mesothelioma as well as other cancers and tuberculosis. While it may not be useful for diagnosis, higher osteopontin levels can indicate a worse prognosis.
Some of these tests are already available, but others are still in development. Health care professionals may eventually use some of these tests to screen for mesothelioma in people who have not yet developed any symptoms. Screening tests can help improve outcomes by detecting cancer early, allowing for early treatment.
When you talk to your doctor about mesothelioma, be sure to ask what tests are available. Whether you are seeking a diagnosis, considering treatment options or undergoing treatment, using newer biomarker tests can help you and your doctor make better decisions.