An investigational test based on a panel of 13 protein markers in the blood may be able to detect malignant mesothelioma in people exposed to asbestos, even when the disease is in its earliest stages, according to findings from a study presented at the AACR annual meeting. To conduct the study, researchers used a technology that relies, in part, on DNA molecules called aptamers that bind to proteins in blood samples.
The study used a test developed by Colorado-based SomaLogic (which also funded the study). The test was used to analyze blood samples from 90 patients who had been exposed to asbestos and developed malignant mesothelioma and blood samples from 80 healthy participants who had been exposed to asbestos (control subjects). The research team, led by Dr. Harvey Pass from the New York University Langone Medical Center, used 75 percent of the samples to identify a panel of proteins that were routinely seen in blood samples from patients with mesothelioma but not in samples from the control subjects. Dr. Pass’ laboratory is supported by NCI’s Early Detection Research Network.
The biomarker panel in this “training set” had 80 percent sensitivity and 100 percent specificity for distinguishing between mesothelioma patients and control subjects and detected 15 of the 19 early-stage mesotheliomas, reported Dr. Pass. Similar results were seen in the remaining 25 percent of the samples, known as the validation set. During a press briefing, Dr. Pass also presented data on the test’s performance in a different blinded validation set of samples from 38 patients with asbestos-related mesothelioma and 62 healthy asbestos-exposed control subjects. In this set, the marker panel had 92 percent specificity and 92 percent sensitivity.
In most patients with malignant mesothelioma, the disease is typically diagnosed at an advanced stage, when treatment has very limited success. So the ability to detect early-stage disease is important “because these are the people with mesothelioma who will have long-term survival,” Dr. Pass said during the briefing.
The current incidence of malignant mesothelioma is low: approximately 3,000 cases a year in the United States. However, according to Dr. Pass, an estimated 27.5 million people in the United States alone had occupational exposure to asbestos between 1940 and 1979, and because of its long latency period, the incidence of mesothelioma is not expected to peak for another 20 years.
Additional validation studies of the assay are being planned, Dr. Pass said in an interview, and more aptamers are being added to the test in an effort to improve its performance.
NCI Cancer Bulletin for April 5, 2011 - National Cancer Institute
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