Longitudinal Immune Responses to Radiotherapy Differentiate Progression-Free Survival Outcomes in Esophageal Cancer 2309969

Abstract Introduction We hypothesized that baseline immune composition and post-radiotherapy (RT) immune dynamics influence progression-free survival (PFS) in esophageal cancer. Methods Peripheral blood mononuclear cells collected from patients with esophageal adenocarcinoma or squamous cell carcinoma (N = 20, N = 7 progressed, median follow up: 404 days) at baseline, during and immediately post-RT, as well as ∼days 45 and 180 post-RT were analyzed by mass cytometry. Manual gating followed by cox regression, linear mixed models or unpaired t-test, with Benjamini—Hochberg correction identified associations with PFS. Results At baseline, higher proportions of total CD3+ T cells (HR = 9.66, p = 0.01) and CD4+ central memory T cells (HR = 8.55, p = 0.017) correlated with reduced PFS by cox regression. FOXP3 expression across T cell subsets was similarly linked to reduced PFS (p < 0.05). Radiotherapy induced transient lymphopenia (mean ALC decrease 0.96 K/µL) and expression of activation (HLA-DR, CD38, PD-1, CD95) and proliferation (Ki67) markers across effector, regulatory, and helper T cell subsets (all p < 0.001). Longitudinal analyses revealed that at ∼45 days post-RT, PD-1+ CD8+ T cells (HR 0.10, p = 0.042) and IFNγ CD56hi NK cells (HR 0.082, p = 0.021) were associated with improved PFS, whereas persistence of regulatory (FOXP3+) and terminally differentiated (CD57+ EMRA) phenotypes across CD4+ and CD8+ subsets was associated with progression (p < 0.05). In this initial cohort, baseline immune composition and post-RT immune remodeling distinguished patients with durable tumor control. Conclusion Patients who progressed exhibited a more regulatory immune profile at baseline that persists to ∼45 days post-RT. In contrast, immune activation across T-cell and innate populations was associated with improved PFS. Ongoing work will expand this cohort (n = 40) and compare differences in immune composition between treatment modalities. Funding Source NCI program grant (P01 CA261669), VIC Innovation Fund and VIC Education Fund Topic Categories Immune Mechanisms of Human Disease (HUM)