The test for soluble mesothelin-related peptides (SMRP) is used to monitor people who have been diagnosed with malignantmesothelioma. It is not used to diagnose the disease.
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
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.
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.
This article was last reviewed on October 21, 2016. | This article was last modified on October 21, 2016.
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