How is it used?
This test is limited to patients who have already been diagnosed with
malignant mesothelioma. It is not used to diagnose the disease. This test is most often used in conjunction with imaging tests such as positron emission tomography (PET) and computed tomography (CT) to:
- determine if you are responding to treatment,
- see if the disease has spread,
- determine if the disease has returned after you have been treated.
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When is it ordered?
A physician might order a series of SMRP tests to monitor progression of
mesothelioma or its recurrence:
- after you have been diagnosed,
- after you have had surgery to remove tumor tissue in the chest cavity,
- during and/or after chemotherapy or radiation therapy.
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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, you may be responding to therapy. If the levels are unchanged, it may mean that your disease has stabilized.
The interpretation of your SMRP test results will likely be done in conjunction with results from imaging studies. That’s because:
- the test does not always provide physicians with useful information. Patients with other cancers —including lung, ovarian, endometrial, and pancreatic cancers—can have apparent elevated test levels as a result of their cancers producing substances that interfere with the test.
- some patients with epithelial mesothelioma, a form of the disease that affects the cavity lining or membranes, do not produce SMRP.
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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 patient’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
lung function tests (LFTs). Diagnosis may be confirmed by examining tissue from a
biopsy or fluid from the affected area for
malignant cells.
In the US, the Food and Drug Administration has classified the test for SMRP in a special category called a humanitarian device exemption (HDE). The HDE is intended to make medical devices, like laboratory tests, available to patients with rare diseases even though the device has not undergone the usual evaluation for effectiveness. To qualify for a humanitarian device exemption, the device must be intended for use in diseases that occur in fewer than 4000 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 to you and that its probable benefits outweigh any risks. But since HDE tests have not been validated as effective, they are considered experimental. So before you get the test, your physician 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. Your physician will receive certification to use SMRP from that review board.
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