Pleural Fluid May Help Diagnose Mesothelioma

Mesothelin presence in the fluid accumulating in the pleural cavity could be a helpful adjunct to cytology examination in patients with an undiagnosed pleural effusion, according to a new study.

Researchers at Oxford University (UK) prospectively collected fluid samples from 167 patients presenting with pleural effusions. They also measured mesothelin levels in serial pleural fluid samples from another 33 patients who underwent repeated lung drainage and in 32 patients before and after they underwent pleurodesis. Using an enzyme-linked immunosorbent assay, the scientists quantified mesothelin levels in a total of 424 pleural fluid and 64 serum samples. The goal of the study was to evaluate the diagnostic role of mesothelin present in pleural fluid in identifying malignant mesothelioma in these 209 patients, as well as the effect of common clinical factors that could affect measurement accuracy.

The study results showed that in the 24 patients identified with mesothelioma, pleural fluid mesothelin concentrations were significantly higher than in those with metastatic carcinomas and benign effusions. In the diagnosis and exclusion of mesothelioma, mesothelin measurement was superior to cytologic examination. For patients who had "suspicious” cytologic features, pleural fluid mesothelin was found to be 100% specific for mesothelioma. The reliability of mesothelin level measurements remained stable even after pleurodesis or in the presence of bacteria. The study was published in the September 1, 2009, issue of the American Journal of Respiratory and Critical Care Medicine.

"Pleural effusion, or the accumulation of fluid in the pleural cavity, can be maddeningly difficult to diagnose as a wide variety of malignant and benign causes exist,” said lead author Helen Davies, M.D., of the Oxford Centre for Respiratory Medicine. "One of the causes, malignant pleural mesothelioma, is a relatively rare cancer, but its incidence is rapidly increasing on a global scale. This study suggests a way for clinicians to more readily identify these cases from the start.”

"Because mesothelioma has a median survival time of 12 months, minimizing the number of invasive procedures and tests patients require is crucial to reduce morbidity and the time they need to spend in hospital,” Dr. Davies added. "An earlier diagnosis also allows speedier interventions to relieve symptoms as well as initiation of other treatments such as chemotherapy or radiotherapy if appropriate.”

Mesothelioma is a form of cancer that is almost always caused by exposure to asbestos. Malignant cells develop in the mesothelium, a protective lining that covers most of the body's internal organs. Its most common site is the pleura (the outer lining of the lungs and internal chest wall), but it may also occur in the peritoneum, the heart, the pericardium, or in the tunica vaginalis.

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