A set of proteins found in the lung fluid of people with malignant pleural mesothelioma may offer a safer way to diagnose the asbestos cancer in frail or elderly patients.
Mesothelioma is an extremely difficult cancer to diagnose. Accurate diagnosis usually requires a combination of tests including a physical exam, a thorough work history (including possible asbestos exposure), blood or lung fluid tests, imaging scans, and a biopsy.
But not all mesothelioma patients are able to tolerate an invasive procedure such as a thoracoscopy to obtain a tissue sample. For these patients especially, an accurate blood or lung fluid test could be lifesaving.
Protein Biomarkers for Mesothelioma Diagnosis
Researchers in Japan recently evaluated the diagnostic value of two types of protein biomarkers by following the cases of 240 patients who came to the Hyogo Prefectural Amagasaki General Medical Center with suspected pleural mesothelioma between September 2014 and August 2016.
The two types of markers that were the focus of the study were soluble mesothelin-related peptide (SMRP) and cytokeratin 19 fragment/carcinoembryonic antigen (CYFRA 21-1/CEA). Both can be found in pleural effusion (lung fluid), which often builds up around the lungs of mesothelioma patients and those with other types of cancer.
The researchers compared the diagnostic accuracy of the two tests to each other, in combination, and with the addition of a CT scan.
Identifying Mesothelioma and Ruling it Out
When compared to each other as a way to help diagnose mesothelioma, the two types of biomarkers brought different things to the table. SMRP was much better at ruling out pleural mesothelioma (specificity) than it was at distinguishing it from other cancers (sensitivity). CYFRA 21-1/CEA, on the other hand, was much better at accurately identifying mesothelioma but not as good at ruling it out.
However, when the two proteins were used in combination, their ability to both accurate identify and rule out malignant pleural mesothelioma jumped significantly.
“The sensitivity and specificity of SMRP combined with the CYFRA 21-1/CEA ratio were 93.8% and 64.9%,” writes researcher Takehiro Otoshi in the American Journal of Respiratory and Critical Care Medicine. Interestingly, the sensitivity of the tests did not change when they were used in combination with CT scanning.
The report concludes, “Combination of these biomarkers helped to rule out malignant pleural mesothelioma effectively among patients at high risk of suffering MPM and would be valuable especially for old frail patients who have difficulty in undergoing invasive procedures such as thoracoscopy.”
Malignant mesothelioma is the most deadly of a group of conditions caused by exposure to asbestos. Most people who are diagnosed with mesothelioma worked in an asbestos industry at some point in their past. While treatment options for mesothelioma are improving, scientists have not found a cure.
Otoshi, T, “Pleural effusion biomarkers and computed tomography findings in diagnosing malignant pleural mesothelioma: A retrospective study in a single center”, October 2, 2017, PLoS One, eCollection 2017