Australian researchers have identified a small molecule that is more prevalent in the blood of people with malignant plural mesothelioma (MPM) than in healthy people. Their findings, presented at the [removed]3rd European Lung Cancer Conference[/removed], are promising as researchers search for more accurate (and earlier) ways to diagnose this deadly lung disease.

Diagnosing mesothelioma now depends on a lung biopsy that contains enough tumor tissue. These biopsies are not always available, however, and physicians can be left uncertain about the patient’s diagnosis, sometimes resulting in delayed treatment.
"If doctors could use a diagnostic marker based on a simple blood test to help with diagnosis, it could circumvent the problem of availability of tumor tissue and help to accelerate the diagnostic process," said Dr Michaela Kirschner from the Asbestos Diseases Research (Concord Hospital Campus) in Sydney, who reported the new findings.

Although a number of proteins have been proposed as blood-based markers for malignant pleural mesothelioma, none of these has so far reached the accuracy required for routine clinical use.

For the study, Kirschner and colleagues explored whether molecules known as microRNAs (miRNAs) in blood could serve as such markers. They compared five patients with MPM and three healthy controls and identified 17 microRNAs that were significantly more abundant in the mesothelioma patients. They validated these miRNAs in a series of blood samples from 15 patients and 13 controls and found that the level of a particular miRNA known as miR-625-3p was four-fold higher in the blood of mesothelioma patients.
Measuring levels of that molecule in blood samples allowed the researchers to discriminate between MPM patients and controls with an accuracy of 82.4%.

Like most diagnostic markers, miR-625-3p is not 100% accurate, according to Kirschner, and there is a chance the assay will produce both false positives as well as false negatives. She recommends further studies on larger sample sizes to see whether the accuracy of miR-625-3p can be confirmed or even turn out to be better than currently observed.
"Should further studies prove that microRNAs in plasma are accurate enough for the diagnosis of malignant pleural mesothelioma, this will lead to the development of a diagnostic test for routine clinical use," Kirschner said. "This test would then represent a relatively simple way to circumvent the problems associated with obtaining a tissue biopsy. For a patient this would mean that appropriate treatment could be instituted at an earlier stage."