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Soluble mesothelin in effusions a strong indicator of mesothelioma

NEW YORK (Reuters Health) - Abnormally high concentrations of soluble mesothelin in pleural and peritoneal effusions are highly suggestive of mesothelioma, investigators in Australia report in the July issue of Thorax.

"Measurement of mesothelin in effusions...might be a useful adjunct to serum analysis in patients with suspected malignancy," Dr. Jenette Creaney, at the University of Western Australia in Nedlands, and associates advise.

Early diagnosis of mesothelioma based on effusions is often difficult because pleural effusions alone may reflect more than 50 systemic or pulmonary disorders. In many cases, cytology may be of limited value either because malignant cells are rare in the effusion or indistinguishable from nonmalignant cells.

Dr. Creaney and associates previously showed that serum levels of mesothelin had high specificity and moderate sensitivity for mesothelioma. Based on these findings, the US Food and Drug Administration has approved the use of serum levels of soluble mesothelin for disease monitoring in mesothelioma.

In an extension of that research, the investigators evaluated mesothelin as a biomarker in pleural or peritoneal effusions.

An ELISA was used to measure mesothelin concentration in pleural fluid from 192 patients. Mesothelioma was diagnosed in 52 cases, other types of malignancies in 56, and benign causes in the remaining 84 cases. Patterns were similar among the 42 patients with peritoneal fluid samples.

Mesothelin levels in effusions of patients with mesothelioma were roughly 7-fold higher than in effusions due to other causes. At a mesothelin concentration cutpoint of 20 nM, specificity was 98% and sensitivity was 67% for distinguishing mesothelioma from non-malignancy.

The investigators observed that, in 10 cases, mesothelin levels were elevated up to 7 months before mesothelioma was diagnosed. "Measurement of mesothelin levels in effusions could facilitate earlier diagnosis," Dr. Creaney's team maintains.