The new test is an enzyme-linked immunosorbent assay (ELISA) system designed to detect the protein N-ERC/mesothelin. N-ERC/mesothelin is overexpressed in mesothelioma and some other types of cancer. ELISA tests use antibodies that change color when they come in contact with a particular substance such as N-ERC/mesothelin.
According to the Japanese researchers who developed and tested the new assay, the previous ELISA system developed in 2008 to detect N-ERC/mesothelin has been “unsatisfactory” and test results were difficult to reproduce. In contrast, the new 7-20 ELISA system produced more accurate positive mesothelioma diagnoses and fewer false negatives.
The team tested the new assay on patients referred to the medical school between June 2005 and March 2013 with suspected mesothelioma. Writing on the findings in Cancer Medicine, lead investigator Tadashi Sato of the Department of Respiratory Medicine at Tokyo’s Juntendo University Graduate School of Medicine reports, “Particularly for the epithelioid type [of mesothelioma], the area under the curve (AUC) and the diagnostic accuracy of N-ERC/mesothelin were excellent.”
The researchers found that the 7-20 ELISA was 95 percent accurate in identifying cases of malignant mesothelioma and 76 percent accurate at ruling out the disease. The test was more reliable when used on blood plasma than on blood serum. The authors note that, in addition to diagnosis, the new test could also be useful for monitoring mesothelioma patients’ response to treatments such as chemotherapy. They say the next step will be to test the usefulness of the new assay in combination with other mesothelioma biomarker tests.
Malignant mesothelioma, an aggressive cancer of body membranes, is one of the most challenging cancers to diagnose, largely because it often causes no symptoms until it is in its later stages.
Sato, T et al, “Newly established ELISA for N-ERC/mesothelin improves diagnostic accuracy in patients with suspected pleural mesothelioma”, Cancer Medicine, June 10, 2014, Epub ahead of print