Abstract 970: Gender-specific stratification of survival following immune checkpoint inhibitor therapy based on intratumoral expression of a B cell gene signature

Despite intensive efforts there is still a great need to identify biomarkers that can accurately identify patients who will obtain the most clinical benefit from immune checkpoint inhibitor (ICI) therapy. High intratumoral CD8+ T cell gene signature (CD8TGS) expression, tumor mutational burden (TMB), and programmed death ligand 1 (PD-L1) expression all enrich for response to ICI treatment across multiple cancer subtypes. Although high intratumoral B cell gene expression also correlated with ICI response in melanoma, whether it adds predictive value in other cancers is unknown. We analyzed tumor RNA sequencing data from the IMvigor 210 phase 2 clinical trial of atezolizumab in patients with advanced urothelial carcinoma to examine potential relationships between B cell gene expression and clinical outcomes. Tumors with high levels of both signatures (BCGS/CD8TS or B8T high/high) had the highest overall survival (OS) of all B8T groups. Surprisingly, the subset of tumors with B8T high/low expression patterns were associated with the worst OS. Moreover, the B8T cell signature stratified patients with high TMB, or high PD-L1, into subsets with differential OS outcomes. Whereas the B8T high/high tumors were associated with the best clinical outcomes in ICI treated men, they were not associated with better OS in ICI treated women. Conversely, women with B8T high/high tumors had the best clinical outcomes in non-ICI treated muscle invasive bladder cancer. Collectively, these data suggest that the B8T signature can enhance OS stratification in patients with advanced urothelial carcinoma who were treated with ICI therapy, and that sex-specific differences in the tumor immune microenvironment may drive disparate outcomes. Citation Format: Adam K. Aragaki, Jean Hoffman-Censits, Noah M. Hahn, David J. McConkey, Burles Avner Johnson. Gender-specific stratification of survival following immune checkpoint inhibitor therapy based on intratumoral expression of a B cell gene signature [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 970.