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Mesothelioma testing is rarely simple or straightforward. Most patients will undergo multiple diagnostic tests to confirm diagnosis or rule out the possibility of mesothelioma. Most diagnostic journeys begin with a physical exam, continue with imaging screenings, and include biopsies of suspected tissues or fluids. Blood tests to look for biomarkers indicative of cancer generally, and mesothelioma specifically, may also be part of the process.
Biomarkers in the Blood
A biomarker is a molecule, of biological origin, found in tissues, blood, or other bodily fluids. These particular molecules are characteristic of some process or disease. Biomarkers are not necessarily bad. For example, certain hormones in urine are biomarkers indicating pregnancy. Biomarkers are also useful in diagnosing diseases including cancer.
Various types of biomarkers can be found in the blood to indicate the presence of cancer in the body. These include proteins, nucleic acids like DNA and RNA, antibodies, and others. If there is a biomarker cancer cells are known to produce, its presence in the blood can be part of an overall diagnosis. Some biomarkers are general to all types of cancers. Others may indicate a specific type.
SMRPs and the MESOMARK Assay
One of the most specific biomarkers for mesothelioma is soluble mesothelin-related protein (SMRP). These proteins are produced and released by cancer cells of the mesothelium. SMRP is normal in mesothelium cells but often overproduced in cancerous cells. The MESOMARK assay is a blood test that measures SMRP levels.
Studies indicate the MESOMARK assay can be a useful diagnostic tool. Most patients with mesothelioma have elevated levels of SMRPs compared to healthy people. Unfortunately, this is not a fool-proof test. Some patients with mesothelioma do not have elevated levels. In addition to diagnosing the cancer, MESOMARK can also be used to track the progress of mesothelioma. In patients with mesothelioma, levels of SMRP usually go up as the condition worsens.
There is a great potential for SMRP as a biomarker to act as an early test for mesothelioma. People who have been exposed to asbestos could be screened using the assay to detect rising levels of SMRP early, allowing earlier diagnosis and better treatment options.
Another test used to detect mesothelin proteins is the N-ERC/mesothelin test. This test is similar to the MESOMARK assay, but is more accurate thanks to a special enzyme to detect the proteins. While this newer test is more accurate, it is still not a definitive biomarker test.
Another biomarker for mesothelioma is the protein fibulin-3. Like SMRP, this protein is released in larger quantities in mesothelioma cancer cells. The protein can be found in blood and in pleural fluid. One early study using fibulin-3 as a biomarker found it was 95 percent effective at ruling out mesothelioma. Also, the test was more than 96 percent more effective at detecting it. Not all studies have found such promising results, so research is ongoing.
Osteopontin is another protein typically found at higher levels in the blood of patients with mesothelioma. There are, however, other types of cancer that also elevate blood levels of this bone-related protein. These include lung cancer, breast cancer, and colon cancer.
Tests for osteopontin may be most useful in screening people with known asbestos exposure. There is a strong connection between the levels of this biomarker and the extent of asbestos exposure. It may be useful in determining how much exposure a person received, and therefore, the level of risk for developing mesothelioma.
Another potentially useful biomarker is megakaryocyte potentiation factor, or MPF. MPF is a protein made by a precursor of mesothelin. No one yet understands what MPF does in the body. However, it has been detected at elevated levels in people known to have mesothelioma. Other types of cancer may cause elevated levels of MPF, like ovarian and pancreatic cancer.
One study found levels of MPF changed before and after tumor removal surgery. The amount of MPF in the blood varied depending on how much of the tumor could be removed. This means it could be a useful test for determining how much cancerous tissue remains after a surgery.
Tracking Biomarkers in at-Risk Patients
Blood tests for biomarkers have great potential to detect mesothelioma in patients. However, there are limitations. Research continues as scientists seek more accurate tests to specifically diagnose this terrible cancer. In the meantime, these biomarker blood tests help monitor mesothelioma risk in people exposed to asbestos.
Blood tests can be useful for patients exposed to asbestos. For example, your doctor could test regularly for multiple biomarkers, some specific to mesothelioma, others generally for cancer. These tests could help your doctor diagnose cancer in its earliest stages, allowing your better prognosis and treatment options. More research is needed to improve blood tests for mesothelioma biomarkers. However, there is great potential for these improving tests to save more lives.
Page Edited by Patient Advocate Dave Foster
Dave has been a mesothelioma Patient Advocate for over 10 years. He consistently attends all major national and international mesothelioma meetings. In doing so, he is able to stay on top of the latest treatments, clinical trials, and research results. He also personally meets with mesothelioma patients and their families and connects them with the best medical specialists and legal representatives available.