BAP1 loss predicts longer survival for mesothelioma patients treated with pemetrexed-based chemotherapy

BRCA1-associated protein 1 (BAP1) immunohistochemistry (IHC) was assessed as a predictive biomarker for pemetrexed-based treatment in non-surgically treated malignant pleural mesothelioma (MM) patients.IHC was performed on 168 MM patient slides to assess BAP1 loss (BAP1-) or retain (BAP1+). BAP1 mouse monoclonal antibody (C-4) was used. Gender, age, performance status (PS), subtype, types of treatment and overall survival (OS) was retrieved from medical records and registries. Clinical endpoint was OS. Data were analyzed by Fisher´s exact test, Kaplan-Meier estimate, log rank test and cox regression.In total, 91 MM patients that received best supportive care (BSC) and 77 treated with pemetrexed were included in the study (Table 1). Each group was analyzed according to BAP1- or BAP1+. A significantly higher OS was observed in the pemetrexed group for BAP1- versus BAP1+ (OS=20 vs 10 months, p<0.01) even after adjustment for age, sex, PS and subtype (HR=3.5, 95%CI=1.9-6.4, p<0.01) (Figure 1a). BAP1 loss was not prognostic in the BSC group (OS=10.5 vs OS=4 months, p=0.23) (Figure 1b).Loss of BAP1 expression in MM prior to pemetrexed is a significant positive predictive biomarker for OS independent of histological subtype. View this table:FootnotesCite this article as: European Respiratory Journal 2020; 56: Suppl. 64, 4490.This abstract was presented at the 2020 ERS International Congress, in session “Respiratory viruses in the "pre COVID-19" era”.This is an ERS International Congress abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only).