Prognostic Significance of Ki67 Expression in Malignant Peritoneal Mesothelioma.

Objectives:Although Ki67 measurement by immunohistochemistry has been widely used as a prognostic index in cancers, it has not been reported in malignant peritoneal mesothelioma (MPM). Hence, this study examines the prognostic significance of Ki67 in MPM.Methods:Specimens from 42 MPM patients were screened for Ki67 expression using immunohistochemistry. Ki67 expression was classified into 2 groups on the basis of expression (<25%=low; 25%=high) using standard methods. Using Kaplan-Meier survival analysis, the significance of Ki67 was assessed in different clinicopathologic categories.Results:High expression of Ki67 (25% by immunohistochemical evaluation) was correlated with poor survival in the overall group (P=0.001); male sex (P=0.001); female sex (P=0.001); epithelioid tumors (P=0.001): male epithelioid (P=0.001), female epithelioid (P=0.003); peritoneal cancer index (PCI): PCI<20 (P=0.001), PCI20 (P=0.002); and age at diagnosis (AAD): AAD<60 years (P=0.001), AAD60 years (P=0.004). Independent of Ki67, male sex (P=0.007), sarcomatoid histology (P=0.001), PCI20 (P=0.013), and AAD60 years (P=0.004) correlated with poor survival. Multivariate analysis showed that only AAD60 years (P=0.049) and high Ki67 expression for all tumors (P=0.031), male sex (P=0.038), female sex (P=0.021), epithelioid tumors (P=0.044), and AAD<60 years (P=0.029) were statistically significant.Conclusions:Ki67 expression affects prognosis in MPM patients and helps to predict survival within the various clinicopathologic categories.