Soluble Mesothelin-Related Peptide Level Elevation in Mesothelioma Serum and Pleural Effusions

Background Soluble mesothelin-related peptide (SMRP) is a potential marker for malignant pleural mesothelioma (MPM), which may be useful for screening high-risk asbestos-exposed individuals. Methods We evaluated SMRP in serum from MPM patients (n = 90), lung cancer patients (n = 170), age and tobacco-matched asbestos-exposed individuals (n = 66), and in MPM pleural effusions (n = 45), benign effusions (n = 30), and non-MPM effusions (n = 20) using the MesoMark enzyme-linked immunosorbent assay kit (Fujirebio Diagnostics, Malvern, PA). Receiver operating characteristic (ROC) curves were used to define true and false positive rates at various cutoffs. Results Mean serum SMRP levels were higher in MPM compared with lung cancer (5.67 ± 0.82 nM [mean ± standard error of the mean vs 1.99 ± 0.43 nM, p < 0.001), and stage I MPM SMRP levels (n = 12; 2.09 ± 0.41 nM) were significantly higher than those in asbestos-exposed individuals (0.99 ± 0.09 nM, p = 0.02, respectively). Stage 2 to 4 SMRP serum levels were significantly higher than those for stage 1 MPM. The area under the ROC curve for serum SMRP was 0.81 for differentiating MPM and asbestos-exposed individuals; cutoff = 1.9 nM (sensitivity = 60%, specificity = 89%). The MPM pleural effusion SMRP was significantly higher than benign or other non-MPM pleural effusions (65.57 ± 11.33 nM vs 27.46 ± 11.25 nM [p = 0.003] and 18.99 ± 7.48 nM [p = 0.044], respectively). Conclusions These data support SMRP as a promising marker for MPM in both serum and pleural effusion fluid, and justify prospective screening studies of SMRP in combination with other markers for screening of asbestos-exposed cohorts.