Abstract 5709: Variation in Merlin expression and its prognostic significance in malignant pleural mesothelioma

Introduction: Malignant Pleural Mesothelioma (MPM) is an aggressive cancer with overall survival (OS) of about 8 months. Prognostic biomarkers allowing for biology-driven individualized therapies are lacking in MPM. Alterations in a tumor suppressor gene NF-2 are seen in 20-40% of MPM. NF-2 encodes for Merlin, which suppresses tumorigenesis by regulating pathways like mTOR and Hippo. Merlin status had been proposed as a predictive biomarker for treatment with the focal adhesion kinase (FAK) inhibitor. The purpose of our study is to examine differences in Merlin expression among histologic subtypes of MPM and its prognostic impact on clinical outcome. Materials and Method: 48 cases of MPM from 1993-2013 with available archival tissues were identified. H/E stained sections were reviewed by a pathologist and categorized into 3 histologic subtypes, namely epithelioid (E), sarcomatoid (S) and biphasic (B). Immunohisochemistry-based Merlin expression score from 0 to 3 were given to the samples, accounting for both intensity and frequency of staining. Chart review was performed to obtain clinical data. Kruskal-Wallis Test was used to compare mean Merlin scores, and Logrank test was used to compare OS between low Merlin (LM,