Among subjects with a history of asbestos exposure, which is linked to the cancer, only those with mesothelioma turned out to have high levels of the protein. The test is available commercially but not approved for diagnosing the aggressive tumor.
“We’re very enthusiastic that this marker will eventually help the mesothelioma community,” chief author Dr. Harvey Pass of the New York University Langone Medical Center told Reuters Health in a telephone interview. “It’s a first step, but a promising step.”
A next step is to follow patients to see if fibulin-3 levels among high risk patients are elevated in the earliest stages of the disease.
“The problem now is that patients present with late stage bulky disease where we have very few options,” said Dr. Pass. “With an earlier presentation you have a surgical option and better treatment results, and they have better responses to chemotherapy. You can convert this to a disease that you can chronically treat.”
Mesothelioma, relatively rare in the U.S., has a median survival time of 12 months.
“We don’t have a registry of how many are in the United States. We think there are 3,000 or 2,500, and there might be more,” he said.
But, he added, “this is a worldwide problem because we have no idea what the asbestos usage is in China, Japan, Russia and South American. This disease is going to persist and increase as we look into this in other nations.”
An estimated 27 million people just in the U.S. have been exposed to asbestos fibers.
The biomarker studied most extensively to date, soluble mesothelin-related protein, has a sensitivity of 47% and a specificity of 96%.
The new findings were based, in part, on fibulin-3 levels measured in 92 people with mesothelioma, 136 cancer-free volunteers with asbestos exposure, 93 with pleural effusions unrelated to mesothelioma, and 43 health controls.
“Plasma fibulin-3 levels discriminated between stage I or II mesothelioma and asbestos exposure without mesothelioma, at a specificity of 94% and a sensitivity of 100%,” the researchers reported.
“The specificity and sensitivity of fibulin-3 in discriminating between asbestos-exposed persons, as well as patients with effusions not due to mesothelioma, and patients with mesothelioma are superior to those of other published markers, and fibulin-3 levels are not influenced by the duration of asbestos exposure,” the researchers said. “In addition, high levels of fibulin-3 in effusions have a high positive predictive value for the presence of mesothelioma and appear to reflect the prognosis.”
The researchers also found that fibulin-3 levels fell dramatically after reductive surgery and increased as the disease progressed.
Dr. Pass said, “Now that we know this (fibulin-3) protein is elevated in the plasma and pleural effusion, we could combine fibulin-3 with other biomarkers and make it even better. That’s the next step.”
In addition, he said, a longitudinal study would be needed to confirm the usefulness of the test.