The Mesomark blood test for mesothelioma may miss the mark when it comes to diagnosing mesothelioma in its earliest stages.
That is the conclusion of a large new study published in the Journal of Clinical Oncology. The report was a meta-analysis of patients in 16 studies on the value of serum mesothelin as a marker for mesothelioma. The studies included data on 4,491 patients, including 1,026 patients with malignant pleural mesothelioma and various control groups. All were measured for the level of mesothelin in their blood serum using the Mesomark test.
Mesothelin is a protein present in the cells of the mesothelial membrane which surrounds the lungs and other internal organs. However, mesothelin is overexpressed in several types of tumors, including mesothelioma. The Mesomark test, approved by the FDA in 2007 as a humanitarian device, measures blood serum levels of Soluble Mesothelin-Related Peptide (SMRP) and is often used to help distinguish cases of mesothelioma from some other types of cancer.
In their meta-analysis on mesothelin and mesothelioma, the research team found that the sensitivities and specificities of mesothelin in the different studies ranged widely from 19% to 68% and 88% to 100%, respectively. They blame the differences on differences in the study population, the types of control groups used, the stage of the mesothelioma, and the mesothelioma subtype. To determine Mesomark’s value for early diagnosis, they differentiated 217 patients with stage I or II epithelioid and biphasic mesothelioma from 1,612 symptomatic or high-risk controls. At 95% specificity, mesothelin displayed a sensitivity of just 32%
In the summary of their findings, the scientists conclude, “In patients suspected of having mesothelioma, a positive blood test for mesothelin at a high-specificity threshold is a strong incentive to urge further diagnostic steps. However, the poor sensitivity of mesothelin clearly limits its added value to early diagnosis and emphasizes the need for further biomarker research.”
Because mesothelioma has such a poor prognosis, scientists around the world continue to look for other biomarkers that may help detect the cancer earlier. Some of the biomarkers currently under investigation include osteopontin, Angiopoietin-1 (a protein associated with pulmonary fibrosis), serum thioredoxin-1 (a biomarker for rheumatoid arthritis), calretinin (a vitamin-D dependent calcium-binding protein), and the antibodies MMP1 and MMP9.