Abstract LB345: Correlating the blood immune repertoire and clinical features of del17p CLL patients

Abstract Introduction: Deletion in the short arm of chromosome 17 (del17p) is a strong, negative prognostic biomarker found in about eight percent of patients with untreated chronic lymphocytic leukemia (CLL). CLL patients with del17p exhibit resistance to therapy, accelerated disease progression, and global immunodeficiency. It is unclear the extent to which global immunodeficiency impacts disease course and therapy outcomes. The goal of this study was to document the blood immune repertoire of patients with untreated CLL who have del17p and associate with clinical features, time to first treatment (TFT), and overall survival (OS). Methods: Biobanked blood samples from treatment-naïve del17p CLL patients (n = 58) and age-matched controls (n = 5) were obtained. B cells and T cells were analyzed with comprehensive, cell type-specific flow cytometry panels and visualized with unbiased dimensionality reduction. Lab values were log-transformed and compared using t-tests and one-way ANOVAs. TFT was calculated from date of sample collection to date of first CLL-directed therapy or last known untreated date; OS was calculated from date of sample collection to death or last known alive status. Cox proportional hazards regression analyses (results reported as hazard ratio [HR] and 95% confidence interval [CI]) were employed to identify associations of lab values with OS and TFT. Results: Patients with del17p CLL had increased proportions of T regulatory cells (Tregs) among total CD4+ T cells compared to controls (CLL 11.1%, control 5.7%, p = 0.05). A higher proportion of CD8+ T cells was associated with longer TFT (HR 0.57, 95%CI 0.36-0.89); in contrast, higher proportions of TIGIT+ (HR 1.83, 95%CI 1.03-3.28) and TIM3+ conventional (non-Treg) CD4+ T cells were associated with shorter TFT (HR 1.70, 95%CI 1.02-2.84). A higher proportion of PD1+ CD8+ T cells was associated with shorter OS (HR 1.79, 95%CI 1.05-3.06), in addition to PD1+ conventional CD4+ T cell proportion (HR 2.21, 95%CI 1.06-4.60). CLL B cells expressed PD-1 and inducible T cell costimulator (ICOS) at significantly lower median fluorescence intensities (MFIs) than control B cells (p < 0.0001 for both). The CXCR5+ MFI (HR 1.0002, 95%CI 1.0001-1.003) and CD23+ MFI (HR 1.88, 95%CI 1.01-3.50) of CLL B cells were associated with shorter TFT. Discussion: In this cohort of treatment-naïve del17p CLL patients, we determined that patients with higher proportions of exhausted CD4+ and CD8+ T cell phenotypes had significantly shorter OS. Cytotoxic T cell proportion positively associated with TFT, whereas proportions of CD4+ T cell exhaustion phenotypes negatively associated with TFT. Higher CXCR5+ and CD23+ MFIs of CLL B cells also associated with shorter TFT. The preliminary findings from our study suggest that the blood immune repertoire has strong associations with clinically relevant outcomes such as time to first treatment and overall survival in patients with untreated del17p CLL. Citation Format: Ethan J. Katcher, Kim A. Gwin, Sameer A. Parikh, Kari G. Rabe, Petra K. Lothert, Preeti Trisal, Esteban Braggio, Susan L. Slager, Nicholas Strong, Daniel L. Van Dyke, Zhiquan Wang, C. Chris Huang, Anita K. Gandhi, Kay L. Medina, Neil E. Kay. Correlating the blood immune repertoire and clinical features of del17p CLL patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB345.