Impact of BAP1 mutational status on immunotherapy outcomes in advanced malignant pleural mesothelioma: A single institution experience.

Abstract

e20537 Background: Malignant pleural mesothelioma (MPM) is a rare and aggressive tumor of mesothelial cells usually diagnosed at advanced stages with dismal prognosis. Most patients progress after 1st line systemic chemotherapy. In the last decade, single or dual agent immune checkpoint inhibitor (ICI) therapy has emerged as a therapeutic option. BAP1 is a commonly mutated tumor suppressor gene in MPM that has been shown to correlate negatively with survival in other solid tumors. We sought to determine the impact of BAP1 mutation on outcomes with ICIs when used as second line systemic therapy. Methods: We retrospectively reviewed a cohort of MPM patients who received ICIs at the Cleveland Clinic foundation between 2017-2022. Patients must have progressed after 1st line systemic chemotherapy prior to ICI. We then compared oncologic outcomes of ICI therapy based on BAP1 mutational status on Next-Generation Sequencing (NGS). End points of interest were overall response rate (ORR) and progression free survival (PFS) while on ICIs. Results: There were a total of 43 MPM patients who received ICIs following progression on pemetrexed/carboplatin (Median age 74 years, IQR 66-81, range 57-92) with a male predominance (M:F ratio 39:4). Histologies included- 58% epithelioid, 28% sarcomatoid and 14% mixed/biphasic histology. Single agent ICI therapy with nivolumab or pembrolizumab was used in 65%. Median follow up was 3 months. BAP1 mutation on NGS was detected in 16%. Other mutated genes included CDKN2A- 7%, BRAF- 5%, MTAP 2% and PTEN 2%. We compared baseline characteristics and outcomes between BAP1 wild type (WT) and BAP1 mutated (MT) groups. Median age at mesothelioma diagnosis were similar 74 vs 70 years (0.3347) with no significant differences in either asbestos or smoking exposure (Table 1). An analysis of outcomes revealed an ORR to ICI of 33% (36% vs 29% respectively [p = 0.9]). PFS was similar between both groups - 4 months [95% CI, 3-NA] for BAP1 WT vs 4 months [95% CI, 2-18] for BAP1 MT group. Conclusions: BAP1 mutation had no prognostic significance on either response rates or disease progression while on ICI therapy in our cohort of advanced MPM patients. The identification of predictive biomarkers for immunotherapy of MPM is an area of unmet clinical need. [Table: see text]