Prognostic value of tumor infiltrating lymphocytes in epithelioid malignant pleural mesothelioma.

Abstract

e20064 Background: Malignant Mesothelioma (MM) is an aggressive malignancy with survival of 4-12 mo. without treatment and 10% 5-year survival. The response of patients with MM to immunotherapy has increased interest in the tumor immune microenvironment. The purpose of this study was to determine if tumor infiltrating lymphocytes (TIL) are correlated with survival in epithelioid MM. Methods: Immunohistochemistry was performed on specimens from 27 patients with epithelioid mesothelioma using CD4, CD8, and CD68 antibodies. Infiltrate density was scored (0-3+) by pathologist estimate in intratumoral and adjacent tumoral tissue. ANOVA and regression analysis were performed. Overall survival (OS) for the entire group and time to progression (TTP) for nine patients with known time from surgery until tumor recurrence were also studied as a surgical resection subgroup (SRG). Results: For the small SRG the relationship between (TTP) and TIL score of CD8 at the edge of the tumor was significant (F[2,6]=5.64, P=.042) however TIL score of intratumoral CD8 cell infiltrates and TTP did not demonstrate statistical significance. The relationship between OS with CD8 infiltrate at the tumor edge, for the entire group, approached significance at (F [3,22]=2.93, P=0.056). TTP and OS and the TIL score of CD4, CD68 at both tumor center and tumor edge did not demonstrate statistical significance. Conclusions: CD8+ lymphocytes are an important component of host immune defense against cancer. We found that in epithelioid MM the cellular infiltrate of CD8 lymphocytes at the edge of the tumor (but not with intratumoral CD8) was associated with longer time to recurrence. TTP and OS were not associated with CD4 and CD68 within or at the tumor edge. The role of CD8 T-cells and the quantitative difference between CD8 at the edge of tumor and intratumoral CD8 should be further investigated in order to optimize immunotherapy.