Testing for Mesothelioma
Friday, July 1, 2016
Testing for mesothelioma is a long, complex process that typically involves multiple cancer specialists and a series of diagnostic tools. The most widely used tests include imaging scans, biopsies and blood tests.
Imaging scans help doctors visualize abnormal growths on the body’s tissues and organs. Some even show areas with high metabolic activity, which suggest cancer may be present.
The most accurate test for confirming a diagnosis is biopsy, a procedure where doctors remove fluid or tissue samples and study them under a microscope. Researchers also are exploring a variety of blood tests for substances that indicate mesothelioma, but currently none are accurate enough to confirm a diagnosis on their own.
Imaging Tests
Oncologists use imaging tests to check for visible signs of tumors. A mesothelioma diagnosis relies on a series of diagnostic imaging tests, including:
1. X-Rays
Produce basic images of dense areas within the body (such as tumors)
2. CT Scans
Use electromagnetic imagery to create detailed images of internal structures
3. MRIs
Generate images of highly active internal structures using magnets and radio waves
4. PET Scans
Highlight areas of the body that have abnormally high, potentially cancerous metabolic activity
CT scans are most doctors' first choice, while the "gold standard" for mesothelioma diagnosis is a combination CT-PET. However, many mesothelioma diagnoses are made incidentally, when doctors use other types of scans to identify an unknown condition.
Most doctors’ first choice when testing for mesothelioma is a CT scan, but the current “gold standard” is a combination PET-CT scan. With results from both tests, doctors can get a detailed look inside the body and see whether suspicious growths are cancerous or noncancerous. Potentially cancerous growths will light up on PET scans, but not on CT scans or MRIs.
Most of the time, doctors discover mesothelioma incidentally when they use other types of scans to identify an unknown condition.
If you are scheduled for a diagnostic imaging scan:
- Assemble the same personal documents you collected for your first diagnostic appointment.
- Plan for a one- to two-hour appointment.
- Follow any pre-scan guidelines provided by your doctor (such as fasting from food or water).
- Research relaxation techniques if you are nervous about being in an enclosed scanning machine.
- Plan to hear the results from your doctor within one to two weeks of the appointment.
Biopsies
Biopsies are small fluid or tissue samples doctors send to a laboratory for evaluation when testing for mesothelioma. These tests can reveal whether a growth is cancerous, where in the body the cancer originated and what type of cells are involved. The cancer's location and cell type play a major role when it comes to planning treatment.
Blood Tests
In recent years, researchers have spent a considerable amount of time developing mesothelioma blood tests. These tests analyze your blood for proteins and other substances (biomarkers) that are present in mesothelioma patients. Early studies suggest these blood tests have the potential to play a role in testing for mesothelioma, but they are not yet reliable enough to confirm a diagnosis on their own.
All of the mesothelioma blood tests are ELISA-based, meaning enzyme-linked immunosorbent assay, and they use enzymes to detect protein antibodies in blood samples.
The FDA-approved MESOMARK test can detect soluble mesothelin-related peptide (SMRP), a protein and mesothelioma biomarker. Extensive research shows that SMRP is helpful to monitoring tumor response to treatment, but it cannot definitively diagnose mesothelioma.
Too many false positives are recorded and some cases of cancer go undetected using MESOMARK. The test’s potential to screen for mesothelioma among people exposed to asbestos is questionable as well; one study found it helpful at identifying persons at risk of mesothelioma and another study did not.
The SOMAmer test can detect more than 1,000 proteins in blood serum, and these proteins may have diagnostic value in identifying mesothelioma. A 2012 study analyzed blood serum samples from 117 malignant mesothelioma cases and 142 people exposed to asbestos. These samples detected 13 protein biomarkers that helped to accurately identify malignant mesothelioma.
The test accurately detected malignant mesothelioma in 90 percent of cases and ruled out the cancer in 95 percent of people without the cancer. The biomarker levels correlated with cancer stage, indicating the test may have value in monitoring the progress of mesothelioma. Continued analysis of more cases of mesothelioma is needed to validate the worth of the SOMAmer test.
The Human MPF test measures a protein called megakaryocyte potentiation factor (MPF), which is produced by a mesothelin precursor protein. MPF levels increase as mesothelioma tumors grow and are detected in about 91 percent of late-stage patients. The test can rule out mesothelioma in 95 percent of people who don’t have the cancer, but it accurately identifies the cancer in only 64 percent of people with mesothelioma. The test isn’t sensitive enough to help with diagnosis, but it could help doctors monitor the cancer’s progression and response to treatment.