Association of polybromo-associated BAF (PBAF) complex mutations with overall survival (OS) in cancer patients (pts) treated with checkpoint inhibitors (ICIs).

Abstract

103 Background: ICIs have shown benefit across several metastatic carcinomas, yet predictive biomarkers are still lacking. 20% of malignancies harbor alterations in ≥1gene that is part of PBAF complex. With recent data suggesting an association between PBRM1 mutations (mts) and outcomes in renal cell carcinoma (RCC) pts treated with ICIs (Miao, Science, 2018), we examined the association between PBAF mts and OS in ICI-treated patients across several solid cancer (ca) types. Methods: Of 6007 pts with different ca histologies and targeted exome sequencing (Oncopanel) at Dana Farber Cancer institute (DFCI), 138 pts had truncating mts in any PBAF gene (SMARCA4, PBRM1, and ARID2) or oncogenic missense mts in SMARCA4 and were treated with ICIs. 138 histology-matched DFCI pts had none. A publicly-available cohort (2:1 histology matched) from Memorial Sloan Kettering (MSKCC) (Samstein et al., Nature Genetics, 2019) of 621 ca pts (PBAF mutant [MT] = 207, PBAF wild type [WT] = 414) treated with ICIs was analyzed for association between PBAF mts and OS. OS was defined from time from ICI initiation. OS was compared by Cox regression between PBAF MT and PBAF WT. Hazard ratio (HR) was derived using univariable and multivariable analysis (MVA) adjusted for ICI regimen (single vs combination) and age. Results: Median (Md) follow-up for the combined cohort (n = 897) was 27 months (m). Major histologies were non-small cell lung ca (268; 29.9%), melanoma (220; 24.5%), RCC (181; 20.2%), and bladder ca (65; 7.2%). Results on univariable and MVA analyses from individual and combined cohorts are presented below. Conclusions: PBAF mts are associated with survival in ICI-treated ca pts. Work in progress with non-ICI treated pts will determine if this is prognostic or predictive of response. [Table: see text]