Jun 14, 2012 - Searching for a Mesothelioma Blood Test
A new study published recently by the American Society of Clinical Oncology chronicles the hopes and frustration of mesothelioma doctors in search of an easy-to-use, reliable, and inexpensive blood test for mesothelioma. Currently, while certain tests can be used to limit the number of “culprits” behind a patient’s symptoms and may point toward mesothelioma, there is no single blood test that’s both powerful enough and reliable enough to positively identify mesothelioma. Today’s diagnoses are made after surgery or biopsy and during histological staining.
This frustrates many because making a diagnosis of mesothelioma is one of the most difficult due to unspecific symptoms and a long latency period. Not only do the symptoms mimic those of other diseases but patients often wait too long to seek treatment – which significantly endangers their individual prognosis. In addition, existing tests can often lead doctors to misdiagnose the disease and begin courses of treatment that are of no help to a mesothelioma patient.
However, this new study examined blood samples from a wide variety of mesothelioma patients in hopes that some unifying factor could be found and exploited to create a reliable test that could be administered in a timely fashion without the need for biopsy or exploratory surgery.
Specifically the scientists were looking for mesothelin within serum samples. As the study states, “Purpose Mesothelin is currently considered the best available serum biomarker of malignant pleural mesothelioma.” Mesothelin is a protein that exists on the surface of normal mesothelial cells within the human body. However, mesothelioma tumors often overexpress this protein, making its overabundance a solid clue that the individual may be suffering from this specific form of asbestos cancer.
The researchers took a retrospective look at 16 individual diagnostic studies of serum mesothelin (mesothelin in the blood.) All were measured with the Mesomark enzyme-linked assay – a test developed by Fujirebio Diagnostics of Japan.
Data was collected from over 4,400 patients, including 1,026 which had been concretely identified as malignant pleural mesothelioma victims. The data was then corrected for differences between study methodology and the researchers began to look for clues in the individual patient’s serum mesothelin levels.
Using a diagnostic threshold of 2 nanomoles per liter, a unit of measurement used for extremely small concentrations of components within a solution, scientists discovered that “the sensitivities and specificities of mesothelin in the different studies ranged widely from 19% to 68% and 88% to 100%. . .” These varied results were partially attributed to the differences between individual patients age, health history, stage of disease at diagnosis, etc. They also uncovered that the histological type of mesothelioma (epithelioid, sarcomatoid, or biphasic) had a drastic effect of concentrations of mesothelin in the blood.
While the results of the study did confirm that mesothelin within the bloodstream was a positive indicator of mesothelioma, such a discovery could only be used as incentive to undergo further testing. The sensitivity of the compound and the variety in concentrations across the large population of the study revealed that results of mesothelin tests (at least of current tests) were too unreliable to definitely diagnose disease.
While the study did not dispute the use for these serum tests in the diagnostic process, researchers concluded that the possibility of false negatives was too high for them to be relied upon. The study concluded with an open call to other researchers to examine other, potentially more effective biomarkers in the race to create a reliable mesothelioma blood test.
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