Is soluble mesothelin-related protein an upfront predictive marker of pleural mesothelioma? A prospective study on Italian workers exposed to asbestos.

OBJECTIVE: Soluble mesothelin-related peptide (SMRP) may be useful in the diagnosis and detection of early stage mesothelioma. We investigated the SMRP upfront predictive role for mesothelioma in asbestos-exposed workers. METHODS: A total of 1,715 subjects underwent a first visit and were invited for a follow-up after 1 and 2 years, with a clinical examination and blood sampling. SMRP was measured by an ELISA assay. RESULTS: Median SMRP at the first visit was 0.45 [interquartile range (IQR) i.e. 25th-75th percentile: 0.30-0.67 nmol/l]. In all, 1,676 subjects (97.8%) were followed up for a median period of 47.1 months. SMRP was measured at the first visit and at both follow-up visits in 1,536 subjects. At follow-up, 3 subjects were diagnosed with an epithelioid mesothelioma. In these cases, SMRP at the first visit ranged from 0.17 to 0.52 nmol/l. Malignant pleural mesothelioma was diagnosed 9-17 months after the last SMRP evaluation. No SMRP variation was observed during the follow-up. Other 61 miscellaneous cancers were diagnosed (median SMRP at first visit: 0.50 nmol/l, IQR: 0.34-0.71 nmol/l). CONCLUSIONS: Our results did not support the usefulness of SMRP as an early marker for the detection of the disease for a time interval of 1 year.

Individual predictors of increased serum mesothelin in asbestos-exposed workers.

The soluble mesothelin-related peptide (SMRP), a candidate marker for screening of subjects with asbestos exposure, is influenced by some individual and clinical factors. The aim of this study was to quantify the role of age, smoking, weight, presence of diseases and exposure to asbestos on serum SMRP levels in a large series of subjects exposed to asbestos, possible candidates for mesothelioma screening. One thousand seven hundred and four participants underwent clinical examination and were interviewed on medical anamnesis, occupation, smoking and weight. SMRP was measured by an ELISA assay. Overall, median SMRP was 0.4 (IQR 25-75: 0.3-0.7) nmol/l. It was higher in current smokers and in subjects with a cumulative asbestos exposure >50 ff/cc/years than in all the other subjects (p < 0.001 and p = 0.002, respectively). SMRP was positively correlated with age (ρ = 0.11, p < 0.001) and, inversely, with BMI (ρ = -0.15, p < 0.001). SMRP was lower in healthy subjects (n = 1,217: median 0.4 nmol/l) than in subjects with malignant tumors (n = 118: 0.5 nmol/l; p = 0.01), asbestos-related pleural lesions (plaques or thickenings, n = 152: 0.6 nmol/l; p < 0.001) and other benign diseases (n = 182: 0.5 nmol/l; p = 0.04). Multivariate analysis revealed significant predictors of increased SMRP: age >57 years, current smoking, a positive anamnesis for cancer and for asbestos-related pleural lesions, and BMI < 25. Some clinical and demographic variables are associated with serum SMRP levels. The degree of these associations is low, nevertheless they should be accounted for in the interpretation of SMPR as a candidate marker predictive of mesothelioma. The potential predictive value of serum SMRP in screening/surveillance programs must be validated in prospective studies.

Exposure to asbestos: correlation between blood levels of mesothelin and frequency of micronuclei in peripheral blood lymphocytes.

Inhalation of asbestos, a mineral extensively used in a variety of applications, is strongly associated with malignant mesothelioma (MM), a fatal cancer of the pleura. Soluble mesothelin-related peptides (SMRP) are a promising biomarker suggested for the screening of MM in healthy asbestos-exposed subjects. In the present study a comparison of micronucleus (Mn) frequencies in peripheral blood lymphocytes (PBL) between 44 asbestos-exposed and 22 control individuals has been performed, and the correlation with serum SMRP has been examined. SMRP levels were found to be significantly higher in subjects exposed to asbestos and in their various subgroups than in controls. Concerning micronucleated lymphocytes, a statistically significant difference from controls was seen in the percentages of both micronucleated mononucleated lymphocytes (MnMNL) and micronucleated binucleated lymphocytes (MnBNL), but the difference was markedly higher for the percentage of micronucleated polynucleated lymphocytes (MnPNL). With respect to the correlation between the frequency of the three types of micronucleated lymphocytes and serum-SMRP values of asbestos-exposed subjects, it was statistically significant for MnMNL, but not for MnBNL and MnPNL.