Abstract A002: Serum levels of immune markers associated with pathological complete response (pCR) and immune-related adverse events (irAEs) in early-stage breast cancer patients receiving immune checkpoint inhibitor plus chemotherapy in the I-SPY 2 trial
Authors: Alkhafaji Silver , Wolf Denise M. , Basu Amrita , Brown-Swigart Lamorna , Nanda Rita , Liu Minneta , Hirst Gillian L. , Esserman Laura J. , van 't Veer Laura , Campbell Michael 
Published: February 2024

Abstract
Background: Surrogate biomarkers of efficacy and AEs are needed for therapy with immune checkpoint inhibitors (ICI). Although ICI treatments have demonstrated effectiveness in combating early-stage breast cancer (BC), predicting early response and the associated risk of irAEs are important considerations. In this study, we evaluated pre-treatment, early on-treatment, and early changes of serum immune markers in women with BC treated with neoadjuvant chemotherapy plus an ICI. Methods: Serum samples were obtained from 49 women with early stage HER2-negative BC enrolled in the I-SPY 2 trial who received paclitaxel plus an ICI (anti-PD-1) followed by anthracycline/cyclophosphamide. Serum was collected at baseline (T0) and 3 weeks after the first dose (T1). Serum samples were assayed by Ella multiplex immunoassays for 18 pre-selected immune markers, including soluble immune checkpoint molecules (sPD-L1, LAG-3), cytokines (IL-6, IL-8, IFNg, TNFa, IL-10, G-CSF, MCP-1), chemokines (CXCL9, CXCL10, CXCL11, CXCL13), molecules associated with angiogenesis/lymphangiogenesis (VEGF-C), and other markers reflecting immune inflammation/activation (C-Reactive Protein [CRP], CD163, sCD25, GranzymeB). Serum markers showing significant changes from T0 to T1 were identified with the Wilcoxon test. Associations between absolute levels or changes in serum markers and response to therapy (pCR) and/or irAEs were assessed with the Mann–Whitney test. Results: Serum IFNg, G-CSF, IL-10, LAG-3, CCL2, CXCL-10, sCD25, CXCL-9 and CXCL-11 significantly increased between T0 and T1 (P &lt;0.0001, 0.014, &lt;0.001, 0.043, &lt;0.0001, 0.032, &lt;0.0001, &lt;0.0001, &lt;0.0001, respectively). In hormone-receptor positive (HR+)/HER2- patients (N=29), low baseline IFNg serum levels were associated with response to therapy (P = 0.04). In addition, a decrease in sCD25 serum levels from T0 to T1 was strongly associated with response (P = 0.0047) in all HER2- patients. Immune-related AEs were reported for a small number of patients (N=9/49). Increases in serum levels of VEGF-C from T0 to T1 were significantly associated with irAEs (P = 0.0055). In addition, patients who developed irAEs had significantly higher T0 and T1 levels of CD163 (P = 0.022 and 0.024, respectively). Conclusions: Baseline serum level of IFNg and early changes in serum sCD25 levels could be used to monitor and predict clinical benefit from anti-PD-1 agents. This study also suggests that VEGF-C and CD163 may serve as possible candidate prognostic biomarkers for irAEs in patients receiving anti-PD-1 therapy in the early-stage BC setting. While our preliminary results are promising, additional validation in a larger sample size is crucial to confirm the observed trends. Therefore, candidate biomarkers from additional I-SPY 2 arms containing ICIs will be analyzed.
Citation Format: Silver Alkhafaji, Denise M. Wolf, Amrita Basu, Lamorna Brown-Swigart, Rita Nanda, Minneta Liu, Gillian L. Hirst, Laura J. Esserman, Laura van 't Veer, Michael Campbell. Serum levels of immune markers associated with pathological complete response (pCR) and immune-related adverse events (irAEs) in early-stage breast cancer patients receiving immune checkpoint inhibitor plus chemotherapy in the I-SPY 2 trial [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A002.