Background The OXEL study (NCT03487666) is an open label phase II trial for patients with triple negative breast cancer (TNBC) and residual disease after neoadjuvant chemotherapy, who were randomized to receive anti-PD-1 immunotherapy (nivolumab, Arm A), chemotherapy (capecitabine, Arm B), or the combination of immunotherapy and chemotherapy (chemoimmunotherapy, Arm C). We previously reported on the primary endpoint of changes in a peripheral immunoscore based on peripheral blood immune-cell subsets to determine the immunological effects of treatment, and associations with response.¹ Here, we investigate differences in serum analytes, a less labor-intensive methodology than flow-based immune subsets, between patients enrolled in different treatment arms, and define associations with clinical response.

Methods Patients (n=38) were assayed for 97 serum analytes before and after 6 and 12 weeks of treatment using OLINK’s immuno-oncology panel, Meso Scale Discovery, and ELISA assays, for changes with treatment and for associations with disease recurrence and the duration of invasive disease-free survival (iDFS).

Results At baseline, distinct serum analytes were associated with disease recurrence and iDFS in patients receiving immunotherapy or chemotherapy alone. Higher pre-therapy levels of angiogenesis-stimulating growth factor PGF (p=0.0411), purine metabolic enzyme ADA (p=0.0260), and immune checkpoint proteins LAG3 (p=0.0411) and PD-L1 (p=0.0411) associated with disease recurrence after immunotherapy alone. Higher levels of these same analytes at baseline were also associated with shorter iDFS for patients treated with immunotherapy alone. Different analytes, including higher pre-therapy levels of neutrophil-recruiting chemokine CXCL5 (p=0.0480) and pro-inflammatory cytokine TNF (p=0.0480) associated with recurrence for patients treated with chemotherapy alone.

Distinct changes in serum analytes following 6 and 12 weeks were noted with different therapies, including greater increases in chemokines, cytokines, and soluble checkpoint proteins for patients receiving immunotherapy or chemoimmunotherapy compared to chemotherapy alone. Changes in serum analytes were also associated with recurrence and iDFS, with different analytes associating with outcomes depending on whether patients received immunotherapy or chemotherapy. Analyses in patients receiving chemoimmunotherapy more closely resembled those in patients receiving immunotherapy alone than chemotherapy alone, and also showed new associations with outcomes.

Conclusions Patients with TNBC receiving immunotherapy alone or chemoimmunotherapy showed enhanced immune activation compared to patients receiving chemotherapy alone. Distinct baseline and early on-treatment changes in serum analytes were associated with recurrence and iDFS for the different treatment arms. These findings underscore the importance of evaluating soluble proteins in peripheral blood for associations with clinical outcome.

Trial Registration NCT03487666.

Reference

1. Lynce F, Mainor C, Donahue RN, et al. Adjuvant nivolumab, capecitabine or the combination in patients with residual triple-negative breast cancer: the OXEL randomized phase II study. Nat Commun 2024;15:2691. doi: 10.1038/s41467-024-46961-x.

Ethics Approval This study complied with all relevant ethical regulations and was approved by the MedStar Georgetown University Hospital Institutional Review Board.

Consent Written informed consent was obtained from the patient for publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.