German scientists are advancing a new, more reliable blood test that could lead to earlier detection and better prognosis for malignant mesothelioma.
Instead of the typically lengthy and invasive process, the simple blood test could identify early stage disease almost a year before symptoms appear, making it much more treatable.
The advancement stems from a study analyzing a combination of calretinin and mesothelin, two blood-based proteins that are overexpressed when mesothelioma tumors start growing.
“This is a real breakthrough,” biochemist Dr. Georg Johnen, lead study researcher and head of Molecular Medicine at Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, told The Mesothelioma Center at Asbestos.com. “It’s not perfect, but it’s a very important step we’ve taken.”
Scientific Reports published the study last month.
The blood test would allow those at high risk to be monitored regularly and easily.
Occupational exposure to asbestos is the primary cause of mesothelioma, an aggressive cancer with a latency period of 20 to 50 years between first exposure and diagnosis.
Unfortunately, by the time vague symptoms normally appear — shortness of breath, tightness of the chest, dry cough, fluid around the lungs — mesothelioma already is in the latter stages and difficult to treat effectively.
It usually requires a combination of detailed imaging tests and invasive tissue biopsies to make a clinical diagnosis. It also requires an experienced pathologist who is familiar with this rare cancer.
Life expectancy is typically six to 18 months.
Earlier detection could extend survival and save lives by catching the disease when still at a potentially curative stage.
“There is no proof, no study, that proves we could save lives with this,” Johnen said. “That will have to come later, but common sense would tell you that early detection might do that.”
Less than 25 percent of those diagnosed today even qualify for surgery, which is the best chance for long-term survival.
Most patients receive only palliative chemotherapy and radiation.
The blood test utilizes a novel enzyme-linked immunosorbent assay that more effectively detects biomarkers such as calretinin and mesothelin.
The study, done in coordination with Ruhr University Bochum, is the recent culmination of a 10-year surveillance program of the German Social Accident Insurance for Asbestos Workers.
It started with 2,769 healthy participants across Germany who provided blood samples annually in a molecular-marking program.
From the original group, 34 high-risk workers eventually developed cases of malignant mesothelioma.
In retrospect, researchers found the calretinin and mesothelin sensitivity rating was 46 percent, which meant almost half of the cases were detected correctly within 15 months of a clinical diagnosis.
They also found a 98 percent specificity rating, which meant only two percent of those who reached the pre-determined calretinin and mesothelin levels were false positives for mesothelioma.
The average blood-test positive for mesothelioma came 8.6 months before the official diagnosis was made.
Samples were taken as much as 44 months before diagnosis.
This was the first study using the calretinin and mesothelin combination in a prospective cohort.
Earlier studies showing calretinin and mesothelin as reliable biomarkers were done in Mexico and Australia.
The sensitivity rating in Germany increased to 50 percent when the cutoff period was nine months or less. It rose to 56 percent when the testing was done six months or less before diagnosis.
Johnen believes adding a third biomarker to the mix will raise the sensitivity rating considerably — something his research team is already developing.
“In the case for early detection, all we had before were breath tests and X-rays, which were useless,” he said. “This test can accelerate the process of being diagnosed. It’s a good first step.”
The U.S. Food and Drug Administration already approved the mesothelin blood test (under the trade name Mesomark), but not for diagnostic purposes.
It is used today as a monitoring tool. Other biomarkers are used for mesothelioma, but none are consistently reliable.
The new blood test worked best with biphasic and epithelioid cell types of mesothelioma. It did not work for the sarcomatoid subtype, the least common of the three.
Germany has an estimated 1,500 cases of mesothelioma diagnosed each year.
“This may allow you to see elevated marker levels well before you have symptoms,” Johnen said. “This could become very useful.”