Chinese researchers say soluble mesothelin-related peptides (SMRP) in lung fluid is still one of the best biomarkers for mesothelioma, even if it sometimes produces false positives..
SMRP has been studied extensively as a way to help diagnose mesothelioma. The most popular test to check levels of SMRPs in the body is a blood test called MESOMARK. In recent years, other biomarkers for mesothelioma have also emerged.
But SMRPs are not just in the blood. A new meta-analysis of SMRPs from pleural effusions finds that they have a valuable place among top biomarkers for mesothelioma.
Biomarkers for Mesothelioma: SMRPs and Others
Malignant mesothelioma is a type of cancer that starts on the membranes around the lungs, heart or abdomen. SMRPs are produced by the breakdown of proteins in these membranes.
When SMRPs are released by cells in the pleural membrane, some can end up in lung fluid. People with mesothelioma tend to develop excess fluid around their lungs called pleural effusions (PE),
The amount of SMRPs in pleural effusions appears to correlate with the extent of malignant mesothelioma in the body. This is why SMRPs are one of the key biomarkers for mesothelioma.
Some other biomarkers for mesothelioma include osteopontin, fibulin-3 (FBLN3), neutrophil to lymphocyte ratio, c-MET expression, and ki-67 ratios. FBLN3 is most often used for mesothelioma prognosis rather than diagnosis.
Meta-Analysis of Biomarkers for Mesothelioma
A meta-analysis is a study of studies. The current meta-analysis comes from researchers at Capital Medical University in Beijing. Their aim was to evaluate the value of PE-SMRPs among biomarkers for mesothelioma on a larger scale than any single study.
Their meta-analysis included thirteen other studies on SMRP in PE. The studies Included 759 cases of malignant pleural mesothelioma and 1,061 cases of malignant pleural effusion that was not caused by mesothelioma. Another 1,539 cases of pleural effusions had benign causes.
The researchers found that testing SMRPs in pleural effusions diagnosed mesothelioma correctly about 70 percent of the time. The true positive rate is called sensitivity.
The same test was better at ruling out mesothelioma. Testing for SMRPs from pleural effusions correctly ruled out malignant mesothelioma about 90 percent of the time.
“Although the sensitivity of SMRPs was low, PE-SMRPs can be a good indicator of the existence of malignant pleural mesothelioma,” conclude the researchers.
Biomarkers for Mesothelioma are Only Part of the Diagnostic Picture
Not all types of mesothelioma produce high levels of SMRPs. Sarcomatoid mesothelioma produces much less than other types, so SMRP testing may not detect it.
This is one reason that biomarkers for mesothelioma are not the only tool doctors use to diagnose asbestos cancer.
Mesothelioma diagnosis usually also involves imaging studies and histochemical testing of tumor cells. A thorough work history, including any history of asbestos exposure is also important.
About 2,500 Americans receive a mesothelioma diagnosis every year.
Gao, R, et al, “Diagnostic value of soluble mesothelin-related peptides in pleural effusion for malignant pleural mesothelioma: An updated meta-analysis”, April 2019, Medicine, https://insights.ovid.com/crossref?an=00005792-201904050-00016