To monitor progression or recurrence of a rare cancer called mesothelioma that affects the membranes that surround the lungs, heart, and abdominal cavity; most cases of mesothelioma are associated with asbestos exposure.
Soluble Mesothelin-Related Peptides
After you have been diagnosed with mesothelioma, this test may be ordered anytime during or after treatment to follow response to treatment.
A blood sample drawn from a vein in your arm
Soluble mesothelin-related peptides (SMRP) are breakdown products from proteins found in the membranes that line the cavities surrounding the lungs, heart, and abdomen. High amounts of SMRP are often seen in the blood of people suffering from mesothelioma, and the amount of SMRP in the blood is thought to be related to the extent of disease. This test measures the amount of SMRP in the blood.
Malignant mesothelioma is a rare cancer of the membranes that cover the outside of internal organs and line body cavities, including the chest (pleural mesothelioma), abdominal cavity (peritoneal mesothelioma), and the heart (pericardial mesothelioma). About 3,000 new cases are diagnosed annually in the U.S., and pleural mesothelioma is the most common type, accounting for 90% of all cases.
Malignant mesotheliomas can also be classified based on the type of cell found:
- Epithelioid cell type (line body cavities): accounts for 50-70% of mesotheliomas; tends to be associated with a better prognosis than the other types.
- Sarcomatoid cell type: accounts for about 10% of mesotheliomas and is the most difficult to treat.
- Mixed (biphasic): has both epithelioid and sarcomatoid areas; accounts for up to 40% of mesotheliomas.
Most cases of pleural mesothelioma—about 70% to 80%—arise in people with a history of working with asbestos, especially in the shipbuilding, construction, automotive, and fireproofing industries. The disease has a long latency period, meaning that people usually develop mesothelioma 20 to 50 years after asbestos exposure.
How is it used?
Malignant mesothelioma is a rare cancer of the membranes that cover the outside of internal organs and line body cavities, including the chest, abdominal cavity, and the heart. It is usually seen in people who have a history of working with asbestos.
SMRP tests are most often used in conjunction with imaging tests such as positron emission tomography (PET) and computed tomography (CT) to:
- Determine if someone with mesothelioma is responding to treatment
- See if the disease has spread
- Determine if the disease has returned after a person has been treated
When is it ordered?
What does the test result mean?
If a series of SMRP tests show SMRP levels are increasing, it may indicate that mesothelioma has progressed. If the series of tests indicates that SMRP levels are decreasing, then the person may be responding to therapy. If the levels are unchanged, it may mean that the disease has stabilized.
The interpretation of SMRP test results will likely be done in conjunction with results from imaging studies. That is because:
- People with other cancers —including lung, ovarian, endometrial, and pancreatic cancers—can have elevated test levels as a result of their cancers producing substances that interfere with the test.
- Some people with epithelial mesothelioma, a form of the disease that affects the cavity lining or membranes, do not produce SMRP.
Is there anything else I should know?
This test is not used to diagnose mesothelioma but only used to monitor progression or recurrence. The diagnosis of this disease is often difficult and involves many steps. It usually begins with a review of the person's medical history, including a history of exposure to asbestos, and with a complete physical examination. These may be followed by imaging studies of the chest and abdomen, including X-rays and computed tomography (CT) scans, and with pulmonary function tests (PFTs). Diagnosis may be confirmed by examining tissue from a biopsy or fluid from the affected area for malignant cells.
In the U.S., the Food and Drug Administration has classified the test for SMRP in a special category, as a Humanitarian Use Device (HUD), with a Humanitarian Device Exemption (HDE). The HDE is intended to make medical devices, like laboratory tests, available to those with rare diseases even though the device has not undergone the usual evaluation for effectiveness. To qualify for an HDE, the device must be intended for use in diseases that occur in fewer than 4,000 patients per year. These diseases are so rare that it is not cost effective for a manufacturer to do the extensive evaluation needed for FDA approval. The exemption makes a potentially useful device or test available to the small number of people who might benefit from it.
Nonetheless, manufacturers must show that an exempted device doesn't pose any threat of illness or injury and that its probable benefits outweigh any risks. However, since HDE tests have not been validated as effective, they are considered experimental. So, before a person can have an SMRP test performed, the healthcare provider must obtain the approval of an institutional review board (IRB), a committee charged with overseeing medical research involving humans and protecting the rights and welfare of study subjects. The manufacturer of the SMRP test has contracted with a national IRB to provide the review and oversight for this test. The healthcare provider will receive certification to use SMRP from that review board.
What is asbestos and how does it cause mesothelioma?
Asbestos is a heat- and fire-resistant insulating material that was widely used in construction, shipbuilding, and the automotive industry after 1945 and through the 1970s. Workers breathed in the tiny fibers that comprise asbestos. Those fibers entered their pleura, the lining of the chest cavity and lung, and damaged its cells. Mesothelioma develops over a long period of between 20 and 50 years. Research has also shown that family members and others living with workers exposed to asbestos are at an increased risk of developing mesothelioma.
Should everyone have an SMRP test to screen for mesothelioma?
The test is not intended for or useful as a general screening tool but only to help evaluate those who have already been diagnosed with mesothelioma. Since mesothelioma is a very rare cancer, most people will never need to have this test performed.
Can I have the SMRP test done in my healthcare provider's office?
On This Site
Tests: Tumor Markers
Conditions: Lung Diseases
Elsewhere On The Web
National Cancer Institute: Malignant Mesothelioma
The Mesothelioma Group: Mesothelioma Cancer Help
Cleveland Clinic: Mesothelioma
John Hopkins Medicine: Occupational Lung Diseases
Mayo Clinic: Mesothelioma
American Lung Association: Mesothelioma
U.S. Food and Drug Administration: Designating Humanitarian Use Devices, Frequently Asked Questions ( FAQs)
U.S. Food and Drug Administration: Humanitarian Device Exemption